Revert 249626 "Narrow silk pageset to the most plausible content"

Breaks silk benchmarks on all android bots.

Example:
http://build.chromium.org/p/chromium.perf/builders/Android%20Nexus4%20Perf/builds/167/steps/silk/logs/stdio

> Narrow silk pageset to the most plausible content
> 
> This removes a few pages that were duplicative or not mobile-focused enough to
> meet the silk bar. Then, "why" descriptions were added to explain why the page
> is on the pageset. Finallly, it moves a few pages from file urls to
> jankfree.org/silk in order to have them point at image resources.
> 
> R=ernstm
> CC=rschoen
> BUG=340777
> 
> Review URL: https://codereview.chromium.org/140653014

TBR=nduca@chromium.org

Review URL: https://codereview.chromium.org/153563009

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@250048 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 250048