This patch makes the FlutterViewController interface more idiomatic by not
retaining listeners. It's the callers responsibility to make sure the lifetimes
work out.

Tools can send a broadcast intent that will cause Flutter processes to
write their names and observatory ports to the log in JSON format.

* Update to mojo 7d579155cc597aa3befcbfad66eef54bda06b57c

* Update to new API

Previously we'd draw uninitialized memory. Now we draw black.

Fixes #3447

* Close the app after the user acknowledges the Launch Error alert.

This enables the specification of a local engine (via `--local-engine`)
for flutter tools to use.

It crashes. We either need to make it safe to call before
Dart_Initialize on Mac or we need to use some other way of measuring
startup time.

Fixes #4006

When developing the engine from Xcode, it is useful to see log output in Xcode's UI. We were redirecting streams away so that the tools could pick read these logs. With the change to the scheme, when running from Xcode, the logs will show up in Xcode's UI. When, running from the tools, that flag will not be present and the tools will work as they always have.

Earlier, the dynamic service loader was part of the main application
bundle. But now, we package it into Flutter.framework and let the user
control "main". The old path was looking for the manifest in the wrong
spot.

This needs to be updated for the latest Mojo APIs

This patch:

 - makes dart traces (coming from the VM and the timeline API)
   available to mojo:tracing
 - adds --vm-complete-timeline parameter, which makes the Dart VM enable all
   categories of timeline traces from the beginning, allowing to do startup
   tracing

This is based on the equivalent support in dart content handler.

Fixes https://github.com/flutter/flutter/issues/3162.

* Wire up accessibility scrolling

flutter/flutter#1664

* Update to mojo 9a791294e429f9f2ca4f427796a284edb6f6768e

* Update to account for Mojo API changes

* Add mojo service for accessing the system clipboard.

Hooked up for iOS and Android.

BUG=https://github.com/flutter/flutter/issues/1567

We no longer provide the main function for Flutter apps on iOS. Instead, we
just provide Flutter.framework, and the end-developer provides main.

Also, remove unused build rules for building Runner.app. We don't build that
target anymore.

flutter/flutter#1664

* Move node implementation to Objective C

This changes AccessibilityBridge::Node (C++) to be AccessibilityNode (objc)
in order to have the nodes returned directly as ui accessibility elements.
This buys us a few things:

1) We can now return an element tree instead of a flat list, thus negating
   the need to maintain a global rect and global translation
2) We use less memory since we don't need to instantiate both nodes and
   their ensuing accessibility elements
3) accessibility elements can now implement the methods necessary to respond
   to events like user scrolling

https://github.com/flutter/flutter/issues/1664

This patch switches us to building Runner.app on the end-developer's machine,
which will eventually let them customize their app.

Fixes https://github.com/flutter/flutter/issues/3256

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.

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.

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.