SurfaceFlinger: add a crop to the layer state

This change adds a crop rectangle specified in window coordinates to the layer
state.  The all window pixels outside this crop rectangle are treated as though
they were fully transparent.  This change also adds the plumbing necessary for
WindowManager to set that crop.

Change-Id: I582bc445dc8c97d4c943d4db8d582a6ef5a66081
diff --git a/include/private/gui/LayerState.h b/include/private/gui/LayerState.h
index ca277e0..9151c11 100644
--- a/include/private/gui/LayerState.h
+++ b/include/private/gui/LayerState.h
@@ -23,6 +23,7 @@
 #include <utils/Errors.h>
 
 #include <ui/Region.h>
+#include <ui/Rect.h>
 #include <gui/ISurface.h>
 
 namespace android {
@@ -40,6 +41,7 @@
     {
         matrix.dsdx = matrix.dtdy = 1.0f;
         matrix.dsdy = matrix.dtdx = 0.0f;
+        crop.makeInvalid();
     }
 
     status_t    write(Parcel& output) const;
@@ -64,6 +66,7 @@
             uint8_t         mask;
             uint8_t         reserved;
             matrix22_t      matrix;
+            Rect            crop;
             // non POD must be last. see write/read
             Region          transparentRegion;
 };