Adding a flush method to SkCanvas

[junov1, 2012-01-30 14:25:14]

This should help code clarity and brevity in webkit.  There was already a
private flush method in SkDevice. I couldn't find where that method was being
used.

With this change, whenever it is necessary to flush the GrContext in order to
prep a canvas for compositing, we can just call canvas->flush(). If the canvas
happens to be deferred, the deferral queue will be flushed before the GrContext.
 So the use of SkDeferredCanvas will be that much more transparent.  Also, the
code that calls flush no longer has to be ganesh aware.

[reed1, 2012-01-30 14:35:05]

http://codereview.appspot.com/5600044/diff/1/src/core/SkCanvas.cpp
File src/core/SkCanvas.cpp (right):

http://codereview.appspot.com/5600044/diff/1/src/core/SkCanvas.cpp#newcode473
src/core/SkCanvas.cpp:473: void SkCanvas::flush() {
Need to check for null device

[junov1, 2012-01-30 14:39:29]

On 2012/01/30 14:35:05, reed1 wrote:
> Need to check for null device

Done.

[bsalomon, 2012-01-30 14:45:04]

On 2012/01/30 14:39:29, junov1 wrote:
> On 2012/01/30 14:35:05, reed1 wrote:
> > Need to check for null device
> 
> Done.

LGTM

[reed1, 2012-01-30 14:58:26]

lgtm