Implement support for dual source blending in ES

src/gpu/gl/GrGLAssembleInterface.cpp

Index: src/gpu/gl/GrGLAssembleInterface.cpp
diff --git a/src/gpu/gl/GrGLAssembleInterface.cpp b/src/gpu/gl/GrGLAssembleInterface.cpp
index d19b1a30779ecd9ff26b9e064bed88051e5ae1c1..9b07246ef3f7f7d4185d14bb4c9c8d6f52a14809 100644
--- a/src/gpu/gl/GrGLAssembleInterface.cpp
+++ b/src/gpu/gl/GrGLAssembleInterface.cpp
@@ -497,6 +497,11 @@ const GrGLInterface* GrGLAssembleGLESInterface(void* ctx, GrGLGetProc get) {
     GET_PROC(BindTexture);
     GET_PROC_SUFFIX(BindVertexArray, OES);
 
+    if (version >= GR_GL_VER(3,0) && extensions.has("GL_EXT_blend_func_extended")) {
+        GET_PROC_SUFFIX(BindFragDataLocation, EXT);
+        GET_PROC_SUFFIX(BindFragDataLocationIndexed, EXT);
+    }
+
     if (extensions.has("GL_KHR_blend_equation_advanced")) {
         GET_PROC_SUFFIX(BlendBarrier, KHR);
     } else if (extensions.has("GL_NV_blend_equation_advanced")) {