Fix a problem in the matrix convolution image filter exposed by...

Fix a problem in the matrix convolution image filter exposed by https://code.google.com/p/skia/source/detail?r=7152:  when offsetting texture coordinates in a GrEffect, take the origin of the source bitmap origin into account, and flip Y coordinates when we need to.

NOTE:  this will cause the matrixconvolution GM's to need to be rebaselined (again!).

Review URL: https://codereview.appspot.com/7086054

git-svn-id: http://skia.googlecode.com/svn/trunk@7168 2bbb7eff-a529-9590-31e7-b0007b416f81

src/effects/SkMatrixConvolutionImageFilter.cpp

@@ -455,8 +455,9 @@ void GrGLMatrixConvolutionEffect::setData(const GrGLUniformManager& uman,
     GrAssert(effect.kernelSize() == fKernelSize);
     GrAssert(effect.tileMode() == fTileMode);
     float imageIncrement[2];
+    float ySign = texture.origin() == GrSurface::kTopLeft_Origin ? 1.0f : -1.0f;
     imageIncrement[0] = 1.0f / texture.width();
-    imageIncrement[1] = 1.0f / texture.height();
+    imageIncrement[1] = ySign / texture.height();
     uman.set2fv(fImageIncrementUni, 0, 1, imageIncrement);
     uman.set2fv(fTargetUni, 0, 1, effect.target());
     uman.set1fv(fKernelUni, 0, fKernelSize.width() * fKernelSize.height(), effect.kernel());