Add dual source blending support for proper blending with coverage.

Review URL: http://codereview.appspot.com/4535088/



git-svn-id: http://skia.googlecode.com/svn/trunk@1390 2bbb7eff-a529-9590-31e7-b0007b416f81
diff --git a/gpu/src/unix/GrGLDefaultInterface_unix.cpp b/gpu/src/unix/GrGLDefaultInterface_unix.cpp
index ba67065..3e9b975 100644
--- a/gpu/src/unix/GrGLDefaultInterface_unix.cpp
+++ b/gpu/src/unix/GrGLDefaultInterface_unix.cpp
@@ -133,6 +133,7 @@
         GR_GL_GET_PROC(VertexAttribPointer);
         gDefaultInterface.fVertexPointer = glVertexPointer;
         gDefaultInterface.fViewport = glViewport;
+        GR_GL_GET_PROC(BindFragDataLocationIndexed);
 
         // First look for GL3.0 FBO or GL_ARB_framebuffer_object (same since
         // GL_ARB_framebuffer_object doesn't use ARB suffix.)