Revert 244383 "Use ContextProvider subclass to provide WGC3D poi..."

Revert 244383 "Use ContextProvider subclass to provide WGC3D poi..."

Likely cause of WebGL conformance test crashes on Android GPU bot.

BUG=333761, 181120
> Use ContextProvider subclass to provide WGC3D pointers
> 
> Some cc::ContextProvider instances will also need to provide WebGraphicsContext3D*
> interfaces to the underlying GL context, but not all. This adds a subclass of ContextProvider
> in content:: to use for these users. The compositor itself doesn't need the WGC3D
> accessor so it just uses the base class.
> 
> BUG=181120
> 
> Review URL: https://codereview.chromium.org/126093010

TBR=jamesr@chromium.org

Committed: https://src.chromium.org/viewvc/chrome?view=rev&revision=244470

[Ken Russell (switch to Gerrit), 2014-01-13 07:21:11]

Committed patchset #1 manually as r244470.