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..3a80b3e2d81590865625c1736b295d2b51d9cfe5 100755
--- a/src/gpu/glsl/GrGLSLCaps.h
+++ b/src/gpu/glsl/GrGLSLCaps.h
@@ -74,6 +74,18 @@ public:
 
     bool forceHighPrecisionNDSTransform() const { return fForceHighPrecisionNDSTransform; }
 
+    bool textureSwizzleSupport() const { return fTextureSwizzleSupport; }

[bsalomon, 2015/10/30 17:10:53]

These two seem like features of the API and not of the shading language...
They're used only on the API side.

The way we handle this is tied to our not so great mapping between GL formats
and GrPixelConfigs. I wonder if there is any way to handle this that would add
some flexibility. E.g., could the GLSL caps get populated with a table that
holds four swizzle values for each GrPixelConfig? The GL impl could base the
table on whether R8 is supported and whether texture swizzling is supported.

We currently use texture swizzling to implement R/B swaps for read-/write-pixels
codepaths. I'd be happy to drop that if it could improve this somehow. I doubt
having the extra shader is worth much complexity.

+
+    bool textureRedSupport() const { return fTextureRedSupport; }
+
+    // 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; }
 
     /**
@@ -91,9 +103,13 @@ private:
     bool fUsesPrecisionModifiers : 1;
     bool fCanUseAnyFunctionInShader : 1;
     bool fForceHighPrecisionNDSTransform : 1;
+    bool fTextureSwizzleSupport : 1;
+    bool fTextureRedSupport : 1;
 
     const char* fVersionDeclString;
 
+    const char* fShaderDerivativeExtensionString;
+
     const char* fFBFetchColorName;
     const char* fFBFetchExtensionString;