rework screenshot API and implementation

- SurfaceFlinger now supports to take a screenshot
  directly into an IGraphicBufferProducer

- reimplement the IMemoryHeap screenshot on top
  of the above

- reimplement LayerScreenshot such that its
  BufferQueue is directly used as the destination
  of the screenshot. LayerScreenshot is now a thin
  wrapper around Layer

Bug: 6940974

Change-Id: I69a2096b44b91acbb99eba16f83a9c78d94e0d10
diff --git a/libs/gui/SurfaceComposerClient.cpp b/libs/gui/SurfaceComposerClient.cpp
index e8e208f..edfa78a 100644
--- a/libs/gui/SurfaceComposerClient.cpp
+++ b/libs/gui/SurfaceComposerClient.cpp
@@ -606,6 +606,17 @@
 
 // ----------------------------------------------------------------------------
 
+status_t ScreenshotClient::capture(
+        const sp<IBinder>& display,
+        const sp<IGraphicBufferProducer>& producer,
+        uint32_t reqWidth, uint32_t reqHeight,
+        uint32_t minLayerZ, uint32_t maxLayerZ) {
+    sp<ISurfaceComposer> s(ComposerService::getComposerService());
+    if (s == NULL) return NO_INIT;
+    return s->captureScreen(display, producer,
+            reqWidth, reqHeight, minLayerZ, maxLayerZ);
+}
+
 ScreenshotClient::ScreenshotClient()
     : mWidth(0), mHeight(0), mFormat(PIXEL_FORMAT_NONE) {
 }