Move shader compiling to ProgramBuilder and various ShaderBuilder cleanups.

src/gpu/glsl/GrGLSLCaps.h

Index: src/gpu/glsl/GrGLSLCaps.h
diff --git a/src/gpu/glsl/GrGLSLCaps.h b/src/gpu/glsl/GrGLSLCaps.h
index 4d6f5806674621e7174b6f80ae2c46c1b50e3637..f93ef2766d18f376a0e65c1399ebf6151fbb4502 100755
--- a/src/gpu/glsl/GrGLSLCaps.h
+++ b/src/gpu/glsl/GrGLSLCaps.h
@@ -74,6 +74,14 @@ public:
 
     bool forceHighPrecisionNDSTransform() const { return fForceHighPrecisionNDSTransform; }
 
+    // Returns the string of an extension that must be enabled in the shader to support
+    // derivatives. If nullptr is returned then no extension needs to be enabled. Before calling
+    // this function, the caller should check that shaderDerivativeSupport exists.
+    const char* shaderDerivativeExtensionString() const {
+        SkASSERT(this->shaderDerivativeSupport());
+        return fShaderDerivativeExtensionString;
+    }
+
     GrGLSLGeneration generation() const { return fGLSLGeneration; }
 
     /**
@@ -94,6 +102,8 @@ private:
 
     const char* fVersionDeclString;
 
+    const char* fShaderDerivativeExtensionString;
+
     const char* fFBFetchColorName;
     const char* fFBFetchExtensionString;