Adds a pixel density monitor to the closure labs that can be queried for the current pixel density of a window and dispatches events when it changes.

The pixel densities are mapped to two different modes:
- NORMAL for older screens with a ratio of less than 1.5.
- HIGH for modern screens with a bigger ratio.

Tested on Chrome and FF > 18.

R=chrishenry
DELTA=531 (513 added, 18 deleted, 0 changed)


Revision created by MOE tool push_codebase.
MOE_MIGRATION=6082


git-svn-id: http://closure-library.googlecode.com/svn/trunk@2416 0b95b8e8-c90f-11de-9d4f-f947ee5921c8

[XhrIo] Expose the responseBody property of the XHR object, which is defined in IE. IE 9 can only access binary data from an XHR via this property.

R=brenneman
DELTA=53 (44 added, 3 deleted, 6 changed)


Revision created by MOE tool push_codebase.
MOE_MIGRATION=6083


git-svn-id: http://closure-library.googlecode.com/svn/trunk@2417 0b95b8e8-c90f-11de-9d4f-f947ee5921c8

Change goog.Timer to look for timer methods on goog.global instead of goog.global['window'].

Using goog.global['window'] throws an exception if the domain is escalated after the window reference is saved. 

R=nicksantos
DELTA=15 (0 added, 0 deleted, 15 changed)


Revision created by MOE tool push_codebase.
MOE_MIGRATION=6084


git-svn-id: http://closure-library.googlecode.com/svn/trunk@2418 0b95b8e8-c90f-11de-9d4f-f947ee5921c8