Remove last remnants of back/forward cache

The DocumentWillBecomeInactive ReasonForSuspension is no longer used. This
allows Prerenderer to convert from ActiveDOMObject to just a
DocumentLifecycleObserver. HTMLMediaElement still needs to be an
ActiveDOMObject for hasPendingActivity.

In addition, clean up two manual calls to stopActiveDOMObjects in
FrameLoader.cpp. They predate the call in Document::detach and, in both cases,
Document::detach would shortly be called if it had not been already.

BUG=none

Review URL: https://codereview.chromium.org/26613008

git-svn-id: svn://svn.chromium.org/blink/trunk@159309 bbb929c8-8fbe-4397-9dbb-9b2b20218538
Rename ScriptExecutionContext::Task to ScriptExecutionContextTask

This change moved Task and AddConsoleMessageTask
out from ScriptExecutionContext.

BUG=305497
R=abarth@chromium.org, abarth, tkent

Review URL: https://codereview.chromium.org/26745006

git-svn-id: svn://svn.chromium.org/blink/trunk@159310 bbb929c8-8fbe-4397-9dbb-9b2b20218538
Make AsyncAudioDecoder::decodeAsync() add a reference on audioData argument.

For the following reasons, we need to add a ref on audioData in decodeAsync()
by using RefPtr's constructor, call release() and leakPtr(), create a Task
using the result, and release the ref in AsyncAudioDecoder::notifyComplete().

- When an ArrayBuffer is passed to AudioContext::decodeAudioData(), it's
  already adopted. So, we can't adoptRef() it.
- As decodeAsync() uses postTask(), we need to retain ref on audioData in
  decodeAsync().

BUG=305080

Review URL: https://codereview.chromium.org/26603006

git-svn-id: svn://svn.chromium.org/blink/trunk@159311 bbb929c8-8fbe-4397-9dbb-9b2b20218538
CSS Animations: Clamp interpolation of length values to non-negative where appropriate

Previously blending of lengths were not clamped, unless types were mixed in
which case the output of the timing function was incorrectly clamped to be
between 0 and 1.

Also changes the step between from/to to take place at 50% when either of the values
is undefined.

BUG=305067,302068

Review URL: https://codereview.chromium.org/26237009

git-svn-id: svn://svn.chromium.org/blink/trunk@159314 bbb929c8-8fbe-4397-9dbb-9b2b20218538