Use stencil ops that don't issue writes whenever possible

src/gpu/gl/GrGLGpu.cpp

Index: src/gpu/gl/GrGLGpu.cpp
diff --git a/src/gpu/gl/GrGLGpu.cpp b/src/gpu/gl/GrGLGpu.cpp
index 0945ed565131e78c753ae9095a4269d6414eb48f..b334e2d8f2b72fcc0f0ea930e7063c1f531e7f74 100644
--- a/src/gpu/gl/GrGLGpu.cpp
+++ b/src/gpu/gl/GrGLGpu.cpp
@@ -2118,11 +2118,11 @@ void set_gl_stencil(const GrGLInterface* gl,
         // supported.
         GR_GL_CALL(gl, StencilFunc(glFunc, ref, mask));
         GR_GL_CALL(gl, StencilMask(writeMask));
-        GR_GL_CALL(gl, StencilOp(glFailOp, glPassOp, glPassOp));
+        GR_GL_CALL(gl, StencilOp(glFailOp, GR_GL_KEEP, glPassOp));

[Chris Dalton, 2015/08/18 19:33:11]

I'm not sure it seems correct to modify this part.

Shouldn't we just use the ops supplied in the stencil settings? And if we want
something to be "keep", then the code above this level is responsible to set it
accordingly?

[vbuzinov, 2015/08/21 12:16:57]

Chris, stencil settings don't contain a separate value for depth test fail case,
since skia never uses the depth test.  Effectively we are not changing the
existing behavior here in any way, other than hinting the driver.

     } else {
         GR_GL_CALL(gl, StencilFuncSeparate(glFace, glFunc, ref, mask));
         GR_GL_CALL(gl, StencilMaskSeparate(glFace, writeMask));
-        GR_GL_CALL(gl, StencilOpSeparate(glFace, glFailOp, glPassOp, glPassOp));
+        GR_GL_CALL(gl, StencilOpSeparate(glFace, glFailOp, GR_GL_KEEP, glPassOp));
     }
 }
 }