Use only one GL context per process, share chaches.

Change-Id: Ieabaa25338d2f4b8d4fd90e7401ad6e7452eae11
diff --git a/libs/hwui/GradientCache.h b/libs/hwui/GradientCache.h
index 12c8a23..8795920 100644
--- a/libs/hwui/GradientCache.h
+++ b/libs/hwui/GradientCache.h
@@ -32,6 +32,7 @@
  */
 class GradientCache: public OnEntryRemoved<SkShader*, Texture*> {
 public:
+    GradientCache();
     GradientCache(uint32_t maxByteSize);
     ~GradientCache();