(mostly) working wtf / wtf_unittests gn targets

This adds BUILD.gn targets for Blink's 'wtf' library and the wtf_unittests
executable. They appear to mostly work (at least on mac) with many things
that I don't understand commented out, mostly for windows.

R=thakis

Review URL: https://codereview.chromium.org/25698002

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@229538 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 229538
DevTools: Make Android tabs unloaded from memory accessible via remote debugging protocol (1/3)

Step 1 out of 3:
- added new methods to TabModel interface
  (temporarily non-pure empty implementations to preserve downstream compile)
- removed TabAndroid::android_tab_id_ field and replaced TabAndroid::android_id method with
  TabAndroid::GetAndroidId which directly calls TabBase#getId 
  (temporarily keeping android_id as an alias to GetAndroidId to preserve downstream compile).
- removed tab_id parameter from  TabAndroid::InitWebContents
  (temporarily keeping a bridge method with the old signature to preserve downstream compile).

Further steps:
2. Implement new methods in TabModelImpl and migrate downstream code to the new TabAndroid API.
3. Use the new methods in DevToolsServerDelegate, cleanup migration crutches from Step 1.

BUG=272174

Review URL: https://codereview.chromium.org/25883010

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@229539 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 229539