Use texture size to determine precision of texture coord varyings.

Review URL: https://codereview.chromium.org/778783002
diff --git a/include/gpu/GrTypesPriv.h b/include/gpu/GrTypesPriv.h
index 0ff4e57..83d8561 100644
--- a/include/gpu/GrTypesPriv.h
+++ b/include/gpu/GrTypesPriv.h
@@ -29,6 +29,15 @@
 };
 static const int kGrSLTypeCount = kLast_GrSLType + 1;
 
+enum GrShaderType {
+    kVertex_GrShaderType,
+    kGeometry_GrShaderType,
+    kFragment_GrShaderType,
+
+    kLastkFragment_GrShaderType = kFragment_GrShaderType
+};
+static const int kGrShaderTypeCount = kLastkFragment_GrShaderType + 1;
+
 /**
  * Gets the vector size of the SLType. Returns -1 for void, matrices, and samplers.
  */