GPU-based blur cleanup.  Clean up some issues raised in code review:

- convolveRect() is too low-level; made it private and exposed convolveInX() and
convolveInY() instead
- added GrAutoTextureEntry to automatically unlock a texture entry
- the clipping and bounder checks were returning false from
drawWithGPUMaskFilter(), causing the software blur to kick in; return true
instead
- the Windows build was giving a spurious warning about reading an uninitialized
variable; rearrange the code to fix it

Review URL:  http://codereview.appspot.com/4710042/



git-svn-id: http://skia.googlecode.com/svn/trunk@1842 2bbb7eff-a529-9590-31e7-b0007b416f81
3 files changed