Add Google Cloud Storage support to the documentation AppEngine server using Cloud Storage official Python client library.

With this CL, URL paths can be directly mapped to Cloud Storage buckets (http://developer.chrome.com/path/... -> gs://bucket/...) using content_storage.json configuration file.

open-source-thrid-party-reviews@ team: this CL adds a third-party library to Chromium repo. The library will be used only in the documentation server and it is the official Google library to access Google Cloud Storage from a Google AppEngine application (docs server).

BUG=338007

Review URL: https://codereview.chromium.org/139303023

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@250663 0039d316-1c4b-4281-b951-d872f2087c98
cc: Only make num_threads - 1 SkPicture clones.

Run on-demand raster on worker threads. This allows us to create
one fewer SkPicture clone as raster will never be done on the
compositor thread.

BUG=333855
TEST=cc_unittests --gtest_filter=LayerTreeHostOnDemandRasterPixelTest.RasterPictureLayer

Review URL: https://codereview.chromium.org/160023002

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@250664 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 250664