Move copy-surface-as-draw fallback to GrGLGpu.

src/gpu/gl/GrGLSL.cpp

Index: src/gpu/gl/GrGLSL.cpp
diff --git a/src/gpu/gl/GrGLSL.cpp b/src/gpu/gl/GrGLSL.cpp
index d388d9120a1d3fc43891ba47a50f2f4221ddb432..f4caf5201292ffbe837129d077fccbbc1d0586b1 100644
--- a/src/gpu/gl/GrGLSL.cpp
+++ b/src/gpu/gl/GrGLSL.cpp
@@ -91,6 +91,25 @@ const char* GrGetGLSLVersionDecl(const GrGLContextInfo& info) {
     }
 }
 
+void GrGLSLAppendDefaultFloatPrecisionDeclaration(GrSLPrecision p, GrGLStandard s, SkString* out) {
+    // Desktop GLSL has added precision qualifiers but they don't do anything.
+    if (kGLES_GrGLStandard == s) {
+        switch (p) {
+            case kHigh_GrSLPrecision:
+                out->append("precision highp float;\n");
+                break;
+            case kMedium_GrSLPrecision:
+                out->append("precision mediump float;\n");
+                break;
+            case kLow_GrSLPrecision:
+                out->append("precision lowp float;\n");
+                break;
+            default:
+                SkFAIL("Unknown precision value.");
+        }
+    }
+}
+
 void GrGLSLMulVarBy4f(SkString* outAppend, const char* vec4VarName, const GrGLSLExpr4& mulFactor) {
     if (mulFactor.isOnes()) {
         *outAppend = SkString();