Ensure we have an EGL context when building layers

Bug #5638421

This bug was introduced by the recent changes that force more frequent
flushes of the GL renderer.

Change-Id: I55dd4ace6ba1e70ab41927150d6c60c37d7fb196

Author: Romain Guy

core/java/android/view/View.java

@@ -10140,7 +10140,11 @@ public void buildLayer() {
 
         switch (mLayerType) {
             case LAYER_TYPE_HARDWARE:
-                getHardwareLayer();
+                if (mAttachInfo.mHardwareRenderer != null &&
+                        mAttachInfo.mHardwareRenderer.isEnabled() &&
+                        mAttachInfo.mHardwareRenderer.validate()) {
+                    getHardwareLayer();
+                }
                 break;
             case LAYER_TYPE_SOFTWARE:
                 buildDrawingCache(true);