Allow PlatformMacMain to be called multiple times

It is called each time the embedder initializes a Flutter view controller. The Mac shell (which does not have a view controller), calls it before NSApplicationMain.

Common items like the base::AtExitManager and the platform message loop are stored in `EmbedderState`

BUILD.gn

@@ -7,8 +7,14 @@ group("default") {
   testonly = true
   deps = [
     "//sky",
-    "//sky/services/dynamic:sdk_lib",
   ]
+
+  if (is_ios) {
+    deps += [
+      "//sky/services/dynamic:sdk_lib",
+      "//sky/shell:flutter_framework",
+    ]
+  }
 }
 
 group("dist") {

sky/shell/platform/ios/flutter_view_controller.mm

@@ -40,11 +40,6 @@
   if (self) {
     _dartBundle = [dartBundleOrNil retain];
 
-    NSBundle* bundle = [NSBundle bundleForClass:[self class]];
-    NSString* icuDataPath = [bundle pathForResource:@"icudtl" ofType:@"dat"];
-
-    sky::shell::PlatformMacMain(0, nullptr, icuDataPath.UTF8String, nullptr);
-
     [self performCommonViewControllerInitialization];
   }
 
@@ -75,6 +70,11 @@
 
   _initialized = YES;
 
+  NSBundle* bundle = [NSBundle bundleForClass:[self class]];
+  NSString* icuDataPath = [bundle pathForResource:@"icudtl" ofType:@"dat"];
+
+  sky::shell::PlatformMacMain(0, nullptr, icuDataPath.UTF8String);
+
   _orientationPreferences = UIInterfaceOrientationMaskAll;
   _dynamicServiceLoader = [[FlutterDynamicServiceLoader alloc] init];
   _viewportMetrics = sky::ViewportMetrics::New();

sky/shell/platform/ios/main_ios.mm

@@ -8,8 +8,9 @@
 #include "sky/shell/platform/mac/platform_mac.h"
 
 int main(int argc, const char* argv[]) {
-  return sky::shell::PlatformMacMain(argc, argv, "", ^() {
-    return UIApplicationMain(argc, (char**)argv, nil,
-                             NSStringFromClass([FlutterAppDelegate class]));
-  });
+  // iOS does use the FlutterViewController that initializes the platform but
+  // we have the command line args here. So call it now.
+  sky::shell::PlatformMacMain(argc, argv, "");
+  return UIApplicationMain(argc, (char**)argv, nil,
+                           NSStringFromClass([FlutterAppDelegate class]));
 }

sky/shell/platform/mac/main_mac.mm

@@ -32,21 +32,21 @@ void AttachMessageLoopToMainRunLoop(void) {
 int main(int argc, const char* argv[]) {
   [SkyApplication sharedApplication];
 
-  return sky::shell::PlatformMacMain(argc, argv, "", ^() {
-    base::CommandLine& command_line = *base::CommandLine::ForCurrentProcess();
-    if (command_line.HasSwitch(sky::shell::switches::kHelp)) {
-      sky::shell::switches::PrintUsage("SkyShell");
-      return EXIT_SUCCESS;
-    }
-
-    if (command_line.HasSwitch(sky::shell::switches::kNonInteractive)) {
-      if (!sky::shell::InitForTesting())
-        return 1;
-      base::MessageLoop::current()->Run();
-      return EXIT_SUCCESS;
-    }
-
-    sky::shell::AttachMessageLoopToMainRunLoop();
-    return NSApplicationMain(argc, argv);
-  });
+  sky::shell::PlatformMacMain(argc, argv, "");
+
+  base::CommandLine& command_line = *base::CommandLine::ForCurrentProcess();
+  if (command_line.HasSwitch(sky::shell::switches::kHelp)) {
+    sky::shell::switches::PrintUsage("SkyShell");
+    return EXIT_SUCCESS;
+  }
+
+  if (command_line.HasSwitch(sky::shell::switches::kNonInteractive)) {
+    if (!sky::shell::InitForTesting())
+      return 1;
+    base::MessageLoop::current()->Run();
+    return EXIT_SUCCESS;
+  }
+
+  sky::shell::AttachMessageLoopToMainRunLoop();
+  return NSApplicationMain(argc, argv);
 }

sky/shell/platform/mac/platform_mac.h

@@ -10,12 +10,7 @@
 namespace sky {
 namespace shell {
 
-typedef int (^PlatformMacMainCallback)(void);
-
-int PlatformMacMain(int argc,
-                    const char* argv[],
-                    std::string icu_data_path,
-                    PlatformMacMainCallback callback);
+void PlatformMacMain(int argc, const char* argv[], std::string icu_data_path);
 
 bool AttemptLaunchFromCommandLineSwitches(sky::SkyEnginePtr& engine);
 

sky/shell/platform/mac/platform_mac.mm

@@ -16,6 +16,7 @@
 #include "base/message_loop/message_loop.h"
 #include "mojo/edk/embedder/embedder.h"
 #include "mojo/edk/embedder/simple_platform_support.h"
+#include "sky/engine/wtf/MakeUnique.h"
 #include "sky/shell/shell.h"
 #include "sky/shell/switches.h"
 #include "sky/shell/tracing_controller.h"
@@ -45,80 +46,60 @@ static void RedirectIOConnectionsToSyslog() {
 #endif
 }
 
-int PlatformMacMainOnce(int argc,
-                        const char* argv[],
-                        std::string icu_data_path,
-                        PlatformMacMainCallback callback) {
-  CHECK([NSThread currentThread] == [NSThread mainThread])
-      << "Platform initialization must occur on the main platform thread";
+class EmbedderState {
+ public:
+  EmbedderState(int argc, const char* argv[], std::string icu_data_path) {
+    RedirectIOConnectionsToSyslog();
 
-  base::mac::ScopedNSAutoreleasePool pool;
+    base::CommandLine::Init(argc, argv);
 
-  base::PlatformThread::SetName("platform_main");
+    InitializeLogging();
 
-  base::AtExitManager exit_manager;
+    base::CommandLine& command_line = *base::CommandLine::ForCurrentProcess();
+    if (command_line.HasSwitch(sky::shell::switches::kTraceStartup)) {
+      // Usually, all tracing within flutter is managed via the tracing
+      // controller
+      // The tracing controller is accessed via the shell instance. This means
+      // that tracing can only be enabled once that instance is created. Traces
+      // early in startup are lost. This enables tracing only in base manually
+      // till the tracing controller takes over.
+      sky::shell::TracingController::StartBaseTracing();
+    }
 
-  RedirectIOConnectionsToSyslog();
+    // This is about as early as tracing of any kind can start. Add an instant
+    // marker that can be used as a reference for startup.
+    TRACE_EVENT_INSTANT0("flutter", "main", TRACE_EVENT_SCOPE_PROCESS);
 
-  bool result = false;
+#if TARGET_OS_IPHONE
+    // One cannot start the message loop on the platform main thread. Instead,
+    // we attach to the CFRunLoop
+    embedder_message_loop_.Attach();
+#endif
 
-  result = base::CommandLine::Init(argc, argv);
-  DLOG_ASSERT(result);
+    mojo::embedder::Init(mojo::embedder::CreateSimplePlatformSupport());
 
-  InitializeLogging();
+    CHECK(gfx::GLSurface::InitializeOneOff());
 
-  base::CommandLine& command_line = *base::CommandLine::ForCurrentProcess();
-  if (command_line.HasSwitch(sky::shell::switches::kTraceStartup)) {
-    // Usually, all tracing within flutter is managed via the tracing controller
-    // The tracing controller is accessed via the shell instance. This means
-    // that tracing can only be enabled once that instance is created. Traces
-    // early in startup are lost. This enables tracing only in base manually
-    // till the tracing controller takes over.
-    sky::shell::TracingController::StartBaseTracing();
+    sky::shell::Shell::InitStandalone(icu_data_path);
   }
 
-  // This is about as early as tracing of any kind can start. Add an instant
-  // marker that can be used as a reference for startup.
-  TRACE_EVENT_INSTANT0("flutter", "main", TRACE_EVENT_SCOPE_PROCESS);
-
-  std::unique_ptr<base::MessageLoopForUI> message_loop(
-      new base::MessageLoopForUI());
-
-#if TARGET_OS_IPHONE
-  // One cannot start the message loop on the platform main thread. Instead,
-  // we attach to the CFRunLoop
-  message_loop->Attach();
-#endif
-
-  mojo::embedder::Init(mojo::embedder::CreateSimplePlatformSupport());
-
-  CHECK(gfx::GLSurface::InitializeOneOff());
-  sky::shell::Shell::InitStandalone(icu_data_path);
+ private:
+  base::AtExitManager exit_manager_;
+  base::MessageLoopForUI embedder_message_loop_;
 
-  int exit_code = callback != nullptr ? callback() : EXIT_SUCCESS;
+  DISALLOW_COPY_AND_ASSIGN(EmbedderState);
+};
 
-#if !TARGET_OS_IPHONE
-  if (callback != nullptr) {
-    // If we control the embedder, the callback is what we use to wrap
-    // UIApplicationMain. If we are here, it means that that method has returned
-    // and we need to perform cleanup.
-    message_loop->QuitNow();
-  }
-#endif
+void PlatformMacMain(int argc, const char* argv[], std::string icu_data_path) {
+  CHECK([NSThread isMainThread])
+      << "Embedder initialization must occur on the main platform thread";
 
-  return exit_code;
-}
+  static std::unique_ptr<EmbedderState> g_embedder;
+  static std::once_flag once_main;
 
-int PlatformMacMain(int argc,
-                    const char* argv[],
-                    std::string icu_data_path,
-                    PlatformMacMainCallback callback) {
-  __block int result = EXIT_SUCCESS;
-  static dispatch_once_t onceToken;
-  dispatch_once(&onceToken, ^{
-    result = PlatformMacMainOnce(argc, argv, icu_data_path, callback);
+  std::call_once(once_main, [&]() {
+    g_embedder = WTF::MakeUnique<EmbedderState>(argc, argv, icu_data_path);
   });
-  return result;
 }
 
 static bool FlagsValidForCommandLineLaunch(const std::string& dart_main,