Rename RenderLayerBacking to CompositedLayerMapping

The old name may have been reasonable long ago, but for some time
now, it has been quite a misleading misnomer. RenderLayerBacking
is not a composited backing for a RenderLayer. That role is held by
GraphicsLayers that have drawsContent == true. Instead, this class
manages a small cluster of GraphicsLayers and provides the mapping
between RenderLayer paint phases and GraphicsLayers.

Renaming this will not only be clearer for those who are not
intimately familiar with the Blink compositor code, but it will
also help clarify how this class should evolve further.

BUG=233466

Review URL: https://codereview.chromium.org/25737009

git-svn-id: svn://svn.chromium.org/blink/trunk@158905 bbb929c8-8fbe-4397-9dbb-9b2b20218538
Background color applied on a selection of text is lost when the selection is deleted

While deleting a selection, only inheritable style properties were
saved. Since background color is considered as noninheritable style
property, it was not being saved and hence was lost. Because of this
background color set on a selection of text was lost when the selection
was deleted and if new text is inserted after this it would not have
the background color set.

Before deleting a selection we should save all style properties applied
on that particular selection. Modified accordingly.

NOTE: This patch makes chrome behavior compatible with that of IE and FF.

Review URL: https://codereview.chromium.org/19477010

git-svn-id: svn://svn.chromium.org/blink/trunk@158906 bbb929c8-8fbe-4397-9dbb-9b2b20218538
Delete fast/dom/adopt-node-crash-2.html.

This test is flaky. It relies on autofocus being synchronous. Instead,
it's now async due to lazyAttach. I could make the test unflaky by
adding document.body.offsetHeights in the right places, but I don't really
see the point given that this is a test for a crash that by design
can't happen anymore.

BUG=303321

Review URL: https://codereview.chromium.org/25903003

git-svn-id: svn://svn.chromium.org/blink/trunk@158908 bbb929c8-8fbe-4397-9dbb-9b2b20218538
Fix calc length memory leak

Platfrom calcs were not being properly deref'd and were never freed
after being used in a Length object.
This patch corrects the deref behaviour and avoids the memory leak.

BUG=291498

Review URL: https://codereview.chromium.org/25677002

git-svn-id: svn://svn.chromium.org/blink/trunk@158909 bbb929c8-8fbe-4397-9dbb-9b2b20218538
Revert 158842 "Improve GIF decoding performance"

This broke webkit_unit_tests in Android builds.
See http://build.chromium.org/p/tryserver.chromium/builders/android_dbg_triggered_tests/builds/92328/steps/webkit_unit_tests/logs/stdio

> Improve GIF decoding performance
> 
> This change improves LZW decoding performance for GIF decoding.
> 
> BACKGROUND
> 
> LZW decoding uses a dictionary to store LZW codes. The data structure
> stores the last character for each code and the index of last code.
> This allows back tracing to construct the entire code. Current
> implementation builds the code in reverse order in a temporary buffer
> and then copies it into the row buffer.
> 
> ALGORITHM
> 
> This change eliminates the temporary buffer and saves a memory copy.
> If the code length is known in advance then reconstruction can write
> directly to the row buffer. The index output buffer is advanced by the
> code length, and then reconstruct as usual.
> 
> The code length is saved such that it can be used next time.
> 
> Testing is done locally with a corpus of 70k images. There's no change
> in output and roughly result in a 20% performance gain.
> 
> BUG=233076
> R=pkasting@chromium.org
> 
> Review URL: https://codereview.chromium.org/23646005

TBR=hclam@chromium.org

Review URL: https://codereview.chromium.org/25984002

git-svn-id: svn://svn.chromium.org/blink/trunk@158910 bbb929c8-8fbe-4397-9dbb-9b2b20218538