Reland: cc: Fix size_t to int truncations in layers/ output/ playback/ quads/

cc/output/gl_renderer.cc

Index: cc/output/gl_renderer.cc
diff --git a/cc/output/gl_renderer.cc b/cc/output/gl_renderer.cc
index c695429968234a6efa435bdca50d53067d913b47..b3161bbba57ac37ad25a59624f863f3ce50265ab 100644
--- a/cc/output/gl_renderer.cc
+++ b/cc/output/gl_renderer.cc
@@ -12,6 +12,7 @@
 
 #include "base/logging.h"
 #include "base/memory/scoped_ptr.h"
+#include "base/numerics/safe_conversions.h"
 #include "base/strings/string_split.h"
 #include "base/strings/string_util.h"
 #include "base/strings/stringprintf.h"
@@ -2232,7 +2233,8 @@ void GLRenderer::FlushTextureQuadCache(BoundGeometry flush_binding) {
       static_cast<float*>(&draw_cache_.vertex_opacity_data.front()));
 
   // Draw the quads!
-  gl_->DrawElements(GL_TRIANGLES, 6 * draw_cache_.matrix_data.size(),
+  gl_->DrawElements(GL_TRIANGLES,
+                    6 * base::checked_cast<int>(draw_cache_.matrix_data.size()),

[vmpstr, 2015/06/05 01:03:00]

This is the only checked_cast that I'm using, most other places are
saturated_cast. Let me know if this should change. The code around this is
mostly static_casting everything...

[jschuh, 2015/06/05 14:08:24]

Yeah, it looks like the other locations should be using checked or saturated
cast, but that's fine for a follow on.

[danakj, 2015/06/05 18:22:29]

matrix_data.size() is at most 8 (line 2299). Having a CHECK compiled in here
seems wasteful, and this code is running every frame. I think this should be
DCHECK and static_cast IMO.

wtb base::dchecked_cast heh.

[vmpstr, 2015/06/05 19:27:33]

Ok, I changed this to a DCHECK. I think if this is to be fixed, we should just
do it in one pass for all instances of static_cast in gl_renderer.cc

                     GL_UNSIGNED_SHORT, 0);
 
   // Clear the cache.