Move shader compiling to ProgramBuilder and various ShaderBuilder cleanups.

src/gpu/glsl/GrGLSLCaps.cpp

Index: src/gpu/glsl/GrGLSLCaps.cpp
diff --git a/src/gpu/glsl/GrGLSLCaps.cpp b/src/gpu/glsl/GrGLSLCaps.cpp
index fef5ab377cc9fa667b637c4066db429a3963e8d0..54d041e3a0ebafa5e19594cdbd9da3ba67d287c7 100755
--- a/src/gpu/glsl/GrGLSLCaps.cpp
+++ b/src/gpu/glsl/GrGLSLCaps.cpp
@@ -21,6 +21,7 @@ GrGLSLCaps::GrGLSLCaps(const GrContextOptions& options) {
     fCanUseAnyFunctionInShader = true;
     fForceHighPrecisionNDSTransform = false;
     fVersionDeclString = nullptr;
+    fShaderDerivativeExtensionString = nullptr;
     fFBFetchColorName = nullptr;
     fFBFetchExtensionString = nullptr;
     fAdvBlendEqInteraction = kNotSupported_AdvBlendEqInteraction;