[NaCl SDK] Add simple graphics2d example.

BUG=none
R=sbc@chromium.org, noelallen@chromium.org

Review URL: https://codereview.chromium.org/28613002

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@229587 0039d316-1c4b-4281-b951-d872f2087c98
For debugging/testing, introduce method to switch debug mode dynamically, and set data source. 

Calling initializeDebug() from Dev Console allows flipping debug mode without restarting the browser. 

Testers can use default data source, or override it manually.

Review URL: https://codereview.chromium.org/29833002

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@229588 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 229587
Fix virtual keyboard regression

Add ExtensionWebContentsObserver to virtual keyboard 
web content. Virtual keyboard doesnt have an extension host
nor opened in a browser tab. So we need to specifically add
it. ExtensionWebContentsObserver is introduced in
https://codereview.chromium.org/26538011/

 
BUG=308653

Review URL: https://codereview.chromium.org/29323002

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@229589 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 229589