Adds a bounds parameter to ui::Compositor::ReadPixels

ui/gfx/compositor/compositor_gl.cc

Index: ui/gfx/compositor/compositor_gl.cc
diff --git a/ui/gfx/compositor/compositor_gl.cc b/ui/gfx/compositor/compositor_gl.cc
index e71a0e06a116e610dee3082fb96c3c93a0efa824..14d5c56bcb3ee7eb30143e13812d8741bbf24268 100644
--- a/ui/gfx/compositor/compositor_gl.cc
+++ b/ui/gfx/compositor/compositor_gl.cc
@@ -558,12 +558,15 @@ CompositorGL::~CompositorGL() {
   gl_context_ = NULL;
 }
 
-bool CompositorGL::ReadPixels(SkBitmap* bitmap) {
+bool CompositorGL::ReadPixels(SkBitmap* bitmap, const gfx::Rect& bounds) {
   MakeCurrent();
 
+  if (bounds.right() > size().width() || bounds.bottom() > size().height())
+    return false;
+
   bitmap->setConfig(SkBitmap::kARGB_8888_Config,
-                    size().width(),
-                    size().height());
+                    bounds.width(),
+                    bounds.height());
   bitmap->allocPixels();
   SkAutoLockPixels lock(*bitmap);
   unsigned char* pixels = static_cast<unsigned char*>(bitmap->getPixels());
@@ -575,16 +578,16 @@ bool CompositorGL::ReadPixels(SkBitmap* bitmap) {
   GLint current_alignment = 0;
   glGetIntegerv(GL_PACK_ALIGNMENT, &current_alignment);
   glPixelStorei(GL_PACK_ALIGNMENT, 4);
-  glReadPixels(0,
-               0,
-               size().width(),
-               size().height(),
+  glReadPixels(bounds.x(),
+               size().height() - bounds.y() - bounds.height(),

[Ian Vollick, 2011/11/18 18:13:45]

I think it would be helpful to have a comment like the one in compositor_cc.cc
explaining this flip.

+               bounds.width(),
+               bounds.height(),
                GL_RGBA,
                GL_UNSIGNED_BYTE,
                pixels);
   glPixelStorei(GL_PACK_ALIGNMENT, current_alignment);
 
-  SwizzleRGBAToBGRAAndFlip(pixels, size());
+  SwizzleRGBAToBGRAAndFlip(pixels, bounds.size());
   return true;
 }