Cache the GrEffect used for text rendering in GrBitmapTextContext.

src/gpu/GrCacheable.cpp

Index: src/gpu/GrCacheable.cpp
diff --git a/src/gpu/GrCacheable.cpp b/src/gpu/GrCacheable.cpp
new file mode 100644
index 0000000000000000000000000000000000000000..120be78f0802c69bc26f32d10e038405e656709c
--- /dev/null
+++ b/src/gpu/GrCacheable.cpp
@@ -0,0 +1,17 @@
+/*
+ * Copyright 2014 Google Inc.
+ *
+ * Use of this source code is governed by a BSD-style license that can be
+ * found in the LICENSE file.
+ */
+
+
+#include "GrCacheable.h"
+
+uint32_t GrCacheable::getGenerationID() const {
+    static int32_t gPathRefGenerationID;
+    while (!fGenID) {
+        fGenID = static_cast<uint32_t>(sk_atomic_inc(&gPathRefGenerationID) + 1);
+    }
+    return fGenID;
+}