Caching the result of readPixelsSupported The call was calling GR_GL_GetIntegerv 2 times for each readPixels and thus was causing a loss of performance (resubmit of issue 344793008) Benchmark url: http://packages.gkny.fr/tst/index.html BUG=skia:2681 R=junov@chromium.org Author: piotaixr@chromium.org Review URL: https://codereview.chromium.org/364193004