Remove obsolete "android_src" gyp/gn variable.

Remove obsolete "android_src" gyp/gn variable.

Now that the android webview build uses the NDK there is no longer any
need to refer to the root of the android source tree; remove the
variable to prevent any new uses being introduced.

BUG=

Committed: https://crrev.com/dcdc0932a5809b3e8bdebb81051b429bbf9786fc
Cr-Commit-Position: refs/heads/master@{#301863}

[Torne, 2014-10-29 12:42:51]

torne@chromium.org changed reviewers:
+ cjhopman@chromium.org, mkosiba@chromium.org

[mkosiba (inactive), 2014-10-29 15:39:29]

lgtm

[Torne, 2014-10-29 15:40:20]

The CQ bit was checked by torne@chromium.org

[commit-bot: I haz the power, 2014-10-29 15:41:45]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/692503002/1

[commit-bot: I haz the power, 2014-10-29 15:49:13]

The CQ bit was unchecked by commit-bot@chromium.org

[commit-bot: I haz the power, 2014-10-29 15:49:14]

Try jobs failed on following builders:
  chromium_presubmit on tryserver.chromium.linux
(http://build.chromium.org/p/tryserver.chromium.linux/builders/chromium_presub...)

[Torne, 2014-10-29 15:53:02]

oops, need to wait for cjhopman :)

[cjhopman, 2014-10-29 17:10:11]

lgtm

[Torne, 2014-10-29 17:19:48]

The CQ bit was checked by torne@chromium.org

[commit-bot: I haz the power, 2014-10-29 17:21:12]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/692503002/1

[commit-bot: I haz the power, 2014-10-29 17:26:39]

Committed patchset #1 (id:1)

[commit-bot: I haz the power, 2014-10-29 17:27:52]

Patchset 1 (id:??) landed as
https://crrev.com/dcdc0932a5809b3e8bdebb81051b429bbf9786fc
Cr-Commit-Position: refs/heads/master@{#301863}