Invalidate GrTexture mipmap on content change notification

This fix is necessary to correctly propagate invalidations that
are external to skia. For example, when drawing video or WebGL
into a 2D canvas in Chrome, with mipmaps enabled.

BUG=crbug.com/498356
TEST=GrTextureMipMapInvalidationTest

Review URL: https://codereview.chromium.org/1177843007
5 files changed