* support hot mode from the daemon protocol

* move method params to constructor

This reduces dependence on machine-specific font configuration, making
tests a bit more reproducible.

* Fix covariant overrides in SynchronousFuture.

There were two things going on here. In timeout(), the callback's return
type was needlessly tightened to only allow callbacks that return
futures. This makes SynchronousFuture not substitutable with Future,
whose timeout() allows callbacks that return immediate values.

Since SynchronousFuture.timeout() never calls the callback anyway, I
just loosened it to match Future.timeout().

SynchronousFuture.whenComplete() is just wrong. The type error, again,
is that the callback's return type is too tight. Future.whenComplete()
allows synchronous callbacks.

But the actual implementation is wrong as well. whenComplete() should
return a future that completes to the *original value*, not whatever the
callback returns.

So I just fixed the method to work correctly, including handling
callbacks with synchronous results.

* "(error, stackTrace)" -> "(e, stack)".

* Update examples to lower the deployment target on iOS.

It was widening the return type of a couple of operators compared to
what EquationMember declared it should return. Since it did in fact
always return an Expression, the widening wasn't needed.

This just tightens them to match the base class.

BUG=https://github.com/flutter/flutter/issues/5098

* Remove stray PRODUCT_BUNDLE_IDENTIFIER

This was erroneously added and overrides
the bundle for the gallery causing signing
to fail in my setup.

@chinmaygarde

* Remove PRODUCT_BUNDLE_IDENTIFIER from all Runner pbxproj's

I took the logo_square from:
https://github.com/flutter/identity-assets/tree/master/assets/logo_square
Opened it in preview, gave it a white background
and then dropped it in the icon tool to create
these updated icons.

We may want to use offwhite like we did for Android
but this is sufficient for my demo today.

@hansmuller

We don't yet know how to do this without poping during hero animations.

Now the flexible space bar computes its effect from its size rather than from
the Scaffold's animation.

After this patch, they ignore pointers.

BUG=https://github.com/flutter/flutter/issues/3938

This patch improves the Post and Shrine transitions by making the AppBar
into a Hero and changing the default MaterialPageTransition. Now the
AppBar transitions smoothly between screens and the
MaterialPageTransition doesn't involve a fade effect.

Also, rejigger the bounds of the image header in Pesto to avoid the
"pop" at the end of the animation by laying out the image header at its
final visual size instead of relying on occlusion to size the image
header.

Fixes #5202
Fixes #5204

Why this matters: If you navigate back to a page with a Scrollable that
has a nonzero scrollOffset, we will restore that scrollOffset. We clamp
the scrollOffset to the contentExtent before the first layout, before
contentExtent is updated to its proper value. Initializing contentExtent
to INFINITY effectively disables the first clamp, until we can get a
valid value from layout. Since the previous scrollOffset was valid, it
seems safe to assume it's still valid.

BUG=https://github.com/flutter/flutter/issues/4883
BUG=https://github.com/flutter/flutter/issues/4797

This also required changing the AnimationController state transition
logic to signal completion of the animation during the tick that
finishes the simulation.

Fixes https://github.com/flutter/flutter/issues/3675

Fixes https://github.com/flutter/flutter/issues/5178

These examples should show the best practices for working with
AnimationControllers.

Fixes #5206

Thanks to @leafpetersen for catching these.

Adds Scheduler.debugPrintTransientCallbackRegistrationStack so that you
can find out how your current callback got registered.

* General improvoments to the loader app:
   * Show a message after 8 seconds if no connection comes in.
   * Show a progress bar as files are being uploaded.
   * Hide the spinner just before launching the application.

* General improvements to the "flutter run" UI:
   * Add "?" key as a silent alias for "h".
   * Make the help text bold so it doesn't get mixed with the logs.
   * Make "R" do a cold restart when hot reload is enabled.

* Supporting features and bug fixes:
   * Add support for string service extensions.

* Other bug fixes:
   * Expose debugDumpRenderTree() outside debug mode.
   * Logger.supportsColor was missing a getter.
   * Mention in the usage docs that --hot requires --resident.
   * Trivial style fixes.