Fix clang warnings about struct vs. class.

Change-Id: I9f26cd01ac3153efa6d77a4133686842e2d63203

include/gui/ISurfaceComposer.h

@@ -35,7 +35,7 @@ namespace android {
 
 class ComposerState;
 class DisplayState;
-class DisplayInfo;
+struct DisplayInfo;
 class IDisplayEventConnection;
 class IMemoryHeap;
 

services/surfaceflinger/DisplayDevice.h

@@ -37,7 +37,7 @@ struct ANativeWindow;
 
 namespace android {
 
-class DisplayInfo;
+struct DisplayInfo;
 class DisplaySurface;
 class IGraphicBufferProducer;
 class Layer;

services/surfaceflinger/DisplayHardware/HWComposer.h

@@ -191,7 +191,7 @@ public:
      * This behaves more or less like a forward iterator.
      */
     class LayerListIterator {
-        friend struct HWComposer;
+        friend class HWComposer;
         HWCLayer* const mLayerList;
         size_t mIndex;