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