Fix silent truncations when extracting values from CheckedNumeric

gpu/command_buffer/client/gles2_implementation.cc

 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 // A class to emulate GLES2 over command buffers.
 
 #include "gpu/command_buffer/client/gles2_implementation.h"
 
 #include <GLES2/gl2.h>
 #include <GLES2/gl2ext.h>
@@ skipping 6309 matching lines @@
   // TODO(zmo): Implement client side caching.
   return false;
 }
 
 bool GLES2Implementation::PackStringsToBucket(GLsizei count,
                                               const char* const* str,
                                               const GLint* length,
                                               const char* func_name) {
   DCHECK_LE(0, count);
   // Compute the total size.
-  base::CheckedNumeric<size_t> total_size = count;
+  base::CheckedNumeric<uint32_t> total_size = count;
   total_size += 1;
   total_size *= sizeof(GLint);
   if (!total_size.IsValid()) {
     SetGLError(GL_INVALID_VALUE, func_name, "overflow");
     return false;
   }
   size_t header_size = total_size.ValueOrDefault(0);
   std::vector<GLint> header(count + 1);
   header[0] = static_cast<GLint>(count);
   for (GLsizei ii = 0; ii < count; ++ii) {
@@ skipping 689 matching lines @@
   cached_extensions_.clear();
 }
 
 // Include the auto-generated part of this file. We split this because it means
 // we can easily edit the non-auto generated parts right here in this file
 // instead of having to edit some template or the code generator.
 #include "gpu/command_buffer/client/gles2_implementation_impl_autogen.h"
 
 }  // namespace gles2
 }  // namespace gpu