Pull out shader-specific caps into GrShaderCaps and GrGLSLCaps

BUG=skia:

Review URL: https://codereview.chromium.org/1116713002
diff --git a/src/gpu/GrPrimitiveProcessor.h b/src/gpu/GrPrimitiveProcessor.h
index ea1237b..d66aed1 100644
--- a/src/gpu/GrPrimitiveProcessor.h
+++ b/src/gpu/GrPrimitiveProcessor.h
@@ -67,8 +67,7 @@
 };
 
 class GrIndexBufferAllocPool;
-class GrGLCaps;
-typedef GrGLCaps GrGLSLCaps;
+class GrGLSLCaps;
 class GrGLPrimitiveProcessor;
 class GrVertexBufferAllocPool;