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 faf6bbb0119b0ebbcafb3f9aa5b73b3e44fd3a02..bce832522bf614286134a4e25af2a2444bf0dd49 100644
--- a/cc/output/gl_renderer.cc
+++ b/cc/output/gl_renderer.cc
@@ -2239,8 +2239,11 @@ void GLRenderer::FlushTextureQuadCache(BoundGeometry flush_binding) {
       static_cast<int>(draw_cache_.vertex_opacity_data.size()),
       static_cast<float*>(&draw_cache_.vertex_opacity_data.front()));
 
+  DCHECK_LE(draw_cache_.matrix_data.size(),
+            static_cast<size_t>(std::numeric_limits<int>::max()) / 6u);

[Nico, 2015/07/31 17:57:15]

shouldn't this check that size() is lessequal than 8? StaticGeometry only sets
up indices for at most 8 triangles as far as I can tell.

[vmpstr, 2015/07/31 18:29:31]

Yeah, I think that's clearly a much tighter bound. The intent of this check is
to simply guard against overflow in a call below, so the code is free to have
larger size, if at all possible, as long as it doesn't cause an overflow. But
you're absolutely right that we should probably use as tight of a bound as we
can here.

   // Draw the quads!
-  gl_->DrawElements(GL_TRIANGLES, 6 * draw_cache_.matrix_data.size(),
+  gl_->DrawElements(GL_TRIANGLES,
+                    6 * static_cast<int>(draw_cache_.matrix_data.size()),
                     GL_UNSIGNED_SHORT, 0);
 
   // Clear the cache.