Basic error checking for debugger GL widget.

Currently the debugger segfaults if the GL context cannot be created.
This change allows the debugger to build with GL support, but still run if the
GL context cannot be created at runtime.

R=robertphillips@google.com

Review URL: https://codereview.chromium.org/18275002

git-svn-id: http://skia.googlecode.com/svn/trunk@9834 2bbb7eff-a529-9590-31e7-b0007b416f81
1 file changed