For https://github.com/flutter/flutter/issues/39526

The engine was using a global to store a timestamp representing the
launch of the engine.  This timestamp is initialized with a JNI call
on Android and during shell setup on other platforms.  Later the
timestamp is added to a FlutterEngineMainEnter timeline event used to
measure engine startup time in benchmarks.

This PR removes the global and the JNI call and moves the timestamp
into the settings object.

Since this is currently only meant to be used by the embedding internally, the setter in Objective-C is only exposed via the FlutterDartProject private class extension. Unit tests have been added to the shell_unittests harness.

Fixes https://github.com/flutter/flutter/issues/37641

For https://github.com/flutter/flutter/issues/40686

Unit tests added:
- CacheSkSLWorks
- VisitFilesCanBeCalledTwice
- CanListFilesRecursively

libapp.so contains compiled application Dart code.  On most Android systems,
this library can be loaded by calling dlopen("libapp.so"), which will search
Android's default library directories.

On some Android devices this does not work as expected.  As a workaround, this
patch provides a fallback path to libapp.so based on ApplicationInfo.nativeLibraryDir.

Fixes https://github.com/flutter/flutter/issues/35838

Adds --observatory-host, which allows callers to specify the localhost
IP binding directly. Allows users to set 0.0.0.0 or the host IP address
as is possible in the standalone VM, rather than restricting users to
loopback.

We retain the default behaviour of binding to loopback since the vast
majority of observatory use-cases involve local access (e.g. host tests
on flutter_tester) or port-forwarded local access (e.g. flutter driver
device tests). However, some scenarios, such as QA test labs, may
benefit from binding to a publicly-accessible IP address.

Using it, a Flutter app can monitor missing frames in the release mode, and a custom Flutter runner (e.g., Fuchsia) can add a custom FrameRasterizedCallback.

Related issues:
https://github.com/flutter/flutter/issues/26154
https://github.com/flutter/flutter/issues/31444
https://github.com/flutter/flutter/issues/32447

Need review as soon as possible so we can merge this before the end of May to catch the milestone.

Tests added:
* NoNeedToReportTimingsByDefault
* NeedsReportTimingsIsSetWithCallback
* ReportTimingsIsCalled
* FrameRasterizedCallbackIsCalled
* FrameTimingSetsAndGetsProperly
* onReportTimings preserves callback zone
* FrameTiming.toString has the correct format

This will need a manual engine roll as the TestWindow defined in the framework needs to implement onReportTimings.

This reverts commit 4ead9c8f.

Reland tracked in https://github.com/flutter/flutter/issues/31433.

This reverts commit bd8c5b13.

Reverts flutter/engine#8656

Reason:  https://github.com/flutter/engine/pull/8656 seems to break the framework windows tests and the engine roll (see https://cirrus-ci.com/task/4704667236827136 and https://github.com/flutter/flutter/pull/31330). The failure has been consistent for 7 consecutive engine-to-framework auto-rolls.

TBR: @chinmaygarde 

The callbacks can be wired in via the Settings object. Both runtime and shell unit-tests have been patched to test this.

If the mapping callback is not set or it the callback returns invalid data, ICU initialization will be embedder responsibility.

This affects all embedders and the following have been audited:
* Android: Via a symbol mapping.
* iOS: Via a file mapping.
* Embedder: Via a file mapping.
* Fuchsia: Via a VMO mapping
* Test shells and Flutter tester: Via file mapping with ICU data needing to be next to the executable.

This was used in some embedder implementations. But that was a while ago.

Some components in the Flutter engine were derived from the forked blink codebase. While the forked components have either been removed or rewritten, the use of the blink namespace has mostly (and inconsistently) remained. This renames the blink namesapce to flutter for consistency. There are no functional changes in this patch.

This reverts commit 800ea0a4.

This reverts commit b59c4436.

Revert "Revert "Separate the data required to bootstrap the VM into its own class. (#8397)" (#8406)" (#8414)

This reverts commit f7b4903d.

This reverts commit c9916474.

When attempting to shutdown and subsequently restart the VM, having the
VM own this data introduces lifecycle issues due to circular references.

Allow Flutter to automatically dump the skp that triggers new shader compilations. This is useful for writing custom ShaderWarmUp to reduce jank. By default, it's not enabled to reduce the overhead. This is only available in profile or debug build.

Later, we can add service protocol support to pull the skp from the client to the host. Currently, it works fine for Android-based devices (including our urgent internal clients) where we can `adb shell` into the cache directory.

Link dart:* sources into engine for debugger source support

Currently, dart:* libraries appear to have no source in
debuggers like Observatory. With this change, these sources will be
available in debug mode applications. Sources for dart:* libraries are
lazily loaded on a script-by-script basis.

Refer to https://dart-review.googlesource.com/c/sdk/+/93375 for the Dart
SDK change.

Prior to this the Android embedder code would extract the icudtl.dat asset out
of the APK and write it to local disk during the first startup of the app.

This change will make that work unnecessary and eliminate the risk of ICU
failures due to errors in the extraction process.

Re-land "Wrap the user entrypoint function in a zone with native exception callback. (#7512)" (#7551)

This reverts commit 4c135c29 and applies relevant fixes.