Android WebView: build fixes for use_system_skia.

Android WebView: build fixes for use_system_skia.

The skia shim headers were not being included at the front of the path
because of a gyp processing issue, causing it to pick up the bundled
headers instead by mistake; fix the gyp file.

Also, some of the chromium code depends on non-public headers; add the
required include path for this to work until we can fix the code.

BUG=263818, 274425
Committed: https://src.chromium.org/viewvc/chrome?view=rev&revision=218021

[Torne, 2013-08-16 13:07:54]

Hi Derek, Robert (also martin for committer),

This is the one remaining patch to make use_system_skia work downstream; I've
tested it and everything seems to run just fine. I've filed a bug about the
dependency on private headers.

[robertphillips, 2013-08-16 13:10:13]

lgtm

[commit-bot: I haz the power, 2013-08-16 13:14:22]

No LGTM from a valid reviewer yet. Only full committers are accepted.
Even if an LGTM may have been provided, it was from a non-committer or
a lowly provisional committer, _not_ a full super star committer.
See http://www.chromium.org/getting-involved/become-a-committer
Note that this has nothing to do with OWNERS files.

[mkosiba (inactive), 2013-08-16 13:23:02]

lgtm

[commit-bot: I haz the power, 2013-08-16 13:23:21]

CQ is trying da patch. Follow status at
https://chromium-status.appspot.com/cq/torne@chromium.org/23064007/1

[commit-bot: I haz the power, 2013-08-16 15:28:09]

Change committed as 218021