Now we grab the underlying primative values before exiting the VM.

Partial fix for https://github.com/flutter/flutter/issues/2950

Instead of using a static Activity, we can use the one we get when we construct
the service.

After this patch, main_ios.mm now consumes Flutter.framework via public APIs.
This patch prepares us to move Flutter on iOS over to consuming
Flutter.framework as a binary artifact.

Fixes #https://github.com/flutter/flutter/issues/3689

The flutter tool is now using the observatory's HTTP-based interface

These are now offerred by the Flutter platform services (e.g., SystemChrome,
SystemSound, HapticFeedback).

When there are no pending timers, we should sit in glfwWaitEvents instead of
continuously calling glfwPollEvents. This reduces CPU utilization
significantly.

This reverts commit 5bc5c7b5.

This commit appears to have caused
https://github.com/flutter/flutter/issues/3658

These build definitions no longer work with the current version of FNL. Once
FNL is ready, we'll add new build definitions that work for it again.

Fix handling of backspace in text input.

All the clients of migrated to the new ParagraphConstraints API.

In the new ParagraphConstraints code path, we weren't converting through
LayoutUnit, so we weren't getting the right overflow behavior for extremely
large double values. This resulted in test/rendering/block_test.dart failing.

We don't need to use an explict version of the script snapshotter that is
packaged with the iOS SDK. Instead, we can rely on the flutter command having a
working snapshotter.

All the headers for Flutter.framework are now in framework/Headers and all the
source files for Flutter.framework are now in framework/Source. Previously it
was unclear that FlutterAppDelegate and main_ios.mm weren't part of
Flutter.framework. (They still build as part of the framework, but that's
something I'll fix in a later patch.)

This lets Skia run an optimization pass over the SkPicture before actually
issuing GL commands.

This patch begins to update the Paragraph interface to something sensible. It
introduces a ParagraphConstraints object that is passed to layout() to control
the layout of the paragraph. Once clients are migrated over, the argument will
become required.

Previously the AOT snapshot was packaged as a dynamic library (similar to the
scheme used on iOS).  This change eliminates the need for a native code
toolchain when building for AOT.

Instead of our own shadow copy.

Explicit import instructions in dart:jni

Report Flutter widgets to iOS accessibility API

These were forcing our customers to obey these lints, but not all of our
customers like them. We might enable some of these in the future if they have
concrete benefits (e.g., faster generated code when compiling ahead-of-time).

This include build system changes for selecting Dart's precompiler mode
plus a way to locate and load the precompiled snapshot library from an
Android application

This would have answered a question we received on flutter-dev.

Fixes https://github.com/flutter/flutter/issues/3517

Improve tracing in graphics stack, esp on Mojo

Instead, make Layer::Paint take a new PaintContext that has just exactly
the state that it needs, mirroring PrerollContext. Also, rename
PaintContext to CompositorContext because it holds the context for the
whole compositor.