refactored screenshot code

the core screenshot function now can capture the screen at any lower resolution
performing bilinear filtering.

we also now have some client code to interface with the screenshot service.

it's now possible to request a screenshot at a lower resolution.

Change-Id: I33689bba98507ab928d0898b21596d0d2fe4b953
diff --git a/services/surfaceflinger/SurfaceFlinger.h b/services/surfaceflinger/SurfaceFlinger.h
index f09fdbc..f0a167b 100644
--- a/services/surfaceflinger/SurfaceFlinger.h
+++ b/services/surfaceflinger/SurfaceFlinger.h
@@ -197,7 +197,9 @@
                                                       sp<IMemoryHeap>* heap,
                                                       uint32_t* width,
                                                       uint32_t* height,
-                                                      PixelFormat* format);
+                                                      PixelFormat* format,
+                                                      uint32_t reqWidth,
+                                                      uint32_t reqHeight);
 
             void                        screenReleased(DisplayID dpy);
             void                        screenAcquired(DisplayID dpy);
@@ -318,6 +320,11 @@
             void        commitTransaction();
 
 
+            status_t captureScreenImplLocked(DisplayID dpy,
+                    sp<IMemoryHeap>* heap,
+                    uint32_t* width, uint32_t* height, PixelFormat* format,
+                    uint32_t reqWidth = 0, uint32_t reqHeight = 0);
+
             friend class FreezeLock;
             sp<FreezeLock> getFreezeLock() const;
             inline void incFreezeCount() {