Remove startup flicker on Android (#2733)

According to hackbod on Stack Overflow, we're supposed to block in the
surfaceCreated callback until we've actually drawn into the surface:

http://stackoverflow.com/questions/8772862/surfaceview-flashes-black-on-load/8888108#8888108

sky/shell/gpu/direct/rasterizer_direct.cc

@@ -52,7 +52,8 @@ void RasterizerDirect::ConnectToRasterizer(
   Shell::Shared().AddRasterizer(GetWeakRasterizerPtr());
 }
 
-void RasterizerDirect::OnAcceleratedWidgetAvailable(gfx::AcceleratedWidget widget) {
+void RasterizerDirect::OnAcceleratedWidgetAvailable(gfx::AcceleratedWidget widget,
+                                                    base::WaitableEvent* did_draw) {
   gfx::SurfaceConfiguration config;
   config.stencil_bits = 8;
   surface_ = gfx::GLSurface::CreateViewGLSurface(widget, config);
@@ -66,6 +67,8 @@ void RasterizerDirect::OnAcceleratedWidgetAvailable(gfx::AcceleratedWidget widge
   glClearColor(0.0f, 0.0f, 0.0f, 1.0f);
   glClear(GL_COLOR_BUFFER_BIT);
   surface_->SwapBuffers();
+  if (did_draw)
+    did_draw->Signal();
 }
 
 void RasterizerDirect::Draw(uint64_t layer_tree_ptr,

sky/shell/gpu/direct/rasterizer_direct.h

@@ -6,6 +6,7 @@
 #define SKY_SHELL_GPU_DIRECT_RASTERIZER_H_
 
 #include "base/memory/weak_ptr.h"
+#include "base/synchronization/waitable_event.h"
 #include "flow/compositor_context.h"
 #include "skia/ext/refptr.h"
 #include "sky/shell/gpu/direct/ganesh_canvas.h"
@@ -35,7 +36,8 @@ class RasterizerDirect : public Rasterizer {
   void ConnectToRasterizer(
       mojo::InterfaceRequest<rasterizer::Rasterizer> request) override;
 
-  void OnAcceleratedWidgetAvailable(gfx::AcceleratedWidget widget);
+  void OnAcceleratedWidgetAvailable(gfx::AcceleratedWidget widget,
+                                    base::WaitableEvent* did_draw);
   void OnOutputSurfaceDestroyed();
 
   flow::LayerTree* GetLastLayerTree() override;

sky/shell/gpu/direct/surface_notifications_direct.cc

@@ -14,13 +14,15 @@ namespace sky {
 namespace shell {
 
 void SurfaceNotificationsDirect::NotifyCreated(
-    const PlatformView::Config& config, gfx::AcceleratedWidget widget) {
+    const PlatformView::Config& config,
+    gfx::AcceleratedWidget widget,
+    base::WaitableEvent* did_draw) {
   RasterizerDirect* rasterizer = static_cast<RasterizerDirect*>(config.rasterizer);
   config.ui_task_runner->PostTask(
       FROM_HERE, base::Bind(&UIDelegate::OnOutputSurfaceCreated,
                             config.ui_delegate,
                             base::Bind(&RasterizerDirect::OnAcceleratedWidgetAvailable,
-                                       rasterizer->GetWeakPtr(), widget)));
+                                       rasterizer->GetWeakPtr(), widget, did_draw)));
 }
 
 void SurfaceNotificationsDirect::NotifyDestroyed(

sky/shell/gpu/direct/surface_notifications_direct.h

@@ -5,6 +5,7 @@
 #ifndef SKY_SHELL_GPU_DIRECT_SURFACE_NOTIFICATIONS_DIRECT_H_
 #define SKY_SHELL_GPU_DIRECT_SURFACE_NOTIFICATIONS_DIRECT_H_
 
+#include "base/synchronization/waitable_event.h"
 #include "sky/shell/platform_view.h"
 
 namespace sky {
@@ -13,7 +14,8 @@ namespace shell {
 class SurfaceNotificationsDirect {
  public:
   static void NotifyCreated(const PlatformView::Config& config,
-                            gfx::AcceleratedWidget widget);
+                            gfx::AcceleratedWidget widget,
+                            base::WaitableEvent* did_draw);
   static void NotifyDestroyed(const PlatformView::Config& config);
 };
 

sky/shell/platform/android/platform_view_android.cc

@@ -43,7 +43,7 @@ PlatformView* PlatformView::Create(const Config& config) {
 }
 
 PlatformViewAndroid::PlatformViewAndroid(const Config& config)
-  : PlatformView(config), window_(nullptr) {
+  : PlatformView(config), window_(nullptr), did_draw_(false, false) {
 }
 
 PlatformViewAndroid::~PlatformViewAndroid() {
@@ -65,7 +65,8 @@ void PlatformViewAndroid::SurfaceCreated(JNIEnv* env, jobject obj, jobject jsurf
     base::android::ScopedJavaLocalFrame scoped_local_reference_frame(env);
     window_ = ANativeWindow_fromSurface(env, jsurface);
   }
-  SurfaceNotificationsDirect::NotifyCreated(config_, window_);
+  SurfaceNotificationsDirect::NotifyCreated(config_, window_, &did_draw_);
+  did_draw_.Wait();
 }
 
 void PlatformViewAndroid::SurfaceDestroyed(JNIEnv* env, jobject obj) {

sky/shell/platform/android/platform_view_android.h

@@ -5,6 +5,7 @@
 #ifndef SKY_SHELL_PLATFORM_ANDROID_PLATFORM_VIEW_ANDROID_H_
 #define SKY_SHELL_PLATFORM_ANDROID_PLATFORM_VIEW_ANDROID_H_
 
+#include "base/synchronization/waitable_event.h"
 #include "sky/shell/platform_view.h"
 
 struct ANativeWindow;
@@ -36,6 +37,7 @@ class PlatformViewAndroid : public PlatformView {
   // |Detach|, which will eventually cause |~PlatformViewAndroid|.
   std::unique_ptr<ShellView> shell_view_;
   gfx::AcceleratedWidget window_;
+  base::WaitableEvent did_draw_;
 
   DISALLOW_COPY_AND_ASSIGN(PlatformViewAndroid);
 };

sky/shell/platform/glfw/platform_view_glfw.cc

@@ -21,7 +21,7 @@ PlatformViewGLFW::~PlatformViewGLFW() {}
 void PlatformViewGLFW::SurfaceCreated(gfx::AcceleratedWidget widget) {
   DCHECK(window_ == gfx::kNullAcceleratedWidget);
   window_ = widget;
-  SurfaceNotificationsDirect::NotifyCreated(config_, window_);
+  SurfaceNotificationsDirect::NotifyCreated(config_, window_, nullptr);
 }
 
 void PlatformViewGLFW::SurfaceDestroyed() {

sky/shell/platform/mac/platform_view_mac.mm

@@ -21,7 +21,7 @@ PlatformViewMac::~PlatformViewMac() {}
 void PlatformViewMac::SurfaceCreated(gfx::AcceleratedWidget widget) {
   DCHECK(window_ == gfx::kNullAcceleratedWidget);
   window_ = widget;
-  SurfaceNotificationsDirect::NotifyCreated(config_, window_);
+  SurfaceNotificationsDirect::NotifyCreated(config_, window_, nullptr);
 }
 
 void PlatformViewMac::SurfaceDestroyed() {