Refactor GrGLUniformManager::UniformHandle to initialize itself by default

src/gpu/gl/GrGLUniformManager.h

Index: src/gpu/gl/GrGLUniformManager.h
diff --git a/src/gpu/gl/GrGLUniformManager.h b/src/gpu/gl/GrGLUniformManager.h
index ee693a6a5bba7d8554416a07f5b43b9e9c3504a7..a9cf3ad702ea1b55e2931a695a2af19378652d65 100644
--- a/src/gpu/gl/GrGLUniformManager.h
+++ b/src/gpu/gl/GrGLUniformManager.h
@@ -22,8 +22,27 @@ class SkMatrix;
 class GrGLUniformManager {
 public:
     // Opaque handle to a uniform
-    typedef int UniformHandle;
-    static const UniformHandle kInvalidUniformHandle = 0;
+    class UniformHandle {
+    public:
+        static UniformHandle CreateFromUniformIndex(int i);
+
+        int toUniformIndex() const { GrAssert(isValid()); return ~fHandle; }

[bsalomon, 2013/08/09 13:19:40]

Can we make this private to GrGLUniformManager?

I was thinking either by making it private in UniformHandle and friending
GrGLUniformManager, or by making it a static function of GrGLUniformManager?

The only reason this type really exists is to discourage effect writers from
ever doing their own uploads outside of the manager.

[Kimmo Kinnunen, 2013/08/13 09:00:33]

Done.

+        bool isValid() const { return 0 != fHandle; }
+
+        bool operator==(const UniformHandle& other) const { return other.fHandle == fHandle; }
+
+        UniformHandle()
+            : fHandle(0) {
+        }
+
+    private:
+        UniformHandle(int handle)
+            : fHandle(~handle) {
+            GrAssert(isValid());
+        }
+
+        int fHandle;
+    };
 
     GrGLUniformManager(const GrGLContext& context) : fContext(context) {}