Fix silent truncations when extracting values from CheckedNumeric

gpu/command_buffer/service/gles2_cmd_decoder.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.
 
 #include "gpu/command_buffer/service/gles2_cmd_decoder.h"
 
 #include <limits.h>
 #include <stddef.h>
 #include <stdint.h>
 #include <stdio.h>
@@ skipping 8006 matching lines @@
     base::CheckedNumeric<GLint> src_width_temp = srcX1;
     src_width_temp -= srcX0;
     base::CheckedNumeric<GLint> src_height_temp = srcY1;
     src_height_temp -= srcY0;
     GLuint src_width = 0, src_height = 0;
     if (!src_width_temp.IsValid() || !src_height_temp.IsValid()) {
       LOCAL_SET_GL_ERROR(GL_INVALID_OPERATION, func_name,
                          "the width or height of src region overflow");
       return;
     }
-    src_width = std::abs(src_width_temp.ValueOrDefault(0));
-    src_height = std::abs(src_height_temp.ValueOrDefault(0));
+    if (!src_width_temp.Abs().AssignIfValid(&src_width))
+      src_width = 0;
+    if (!src_height_temp.Abs().AssignIfValid(&src_height))
+      src_height = 0;
 
     gfx::Rect src_region(src_x, src_y, src_width, src_height);
     if (!src_bounds.Contains(src_region) &&
         (src_width != 0) && (src_height != 0)) {
       // If pixels lying outside the read framebuffer, adjust src region
       // and dst region to appropriate in-bounds regions respectively.
       src_bounds.Intersect(src_region);
       GLuint src_real_width = src_bounds.width();
       GLuint src_real_height = src_bounds.height();
       GLuint xoffset = src_bounds.x() - src_x;
@@ skipping 14 matching lines @@
       base::CheckedNumeric<GLint> dst_width_temp = dstX1;
       dst_width_temp -= dstX0;
       base::CheckedNumeric<GLint> dst_height_temp = dstY1;
       dst_height_temp -= dstY0;
       GLuint dst_width = 0, dst_height = 0;
       if (!dst_width_temp.IsValid() || !dst_height_temp.IsValid()) {
         LOCAL_SET_GL_ERROR(GL_INVALID_OPERATION, func_name,
                            "the width or height of dst region overflow");
         return;
       }
-      dst_width = std::abs(dst_width_temp.ValueOrDefault(0));
-      dst_height = std::abs(dst_height_temp.ValueOrDefault(0));
+      if (!dst_width_temp.Abs().AssignIfValid(&dst_width))
+        dst_width = 0;
+      if (!dst_height_temp.Abs().AssignIfValid(&dst_height))
+        dst_height = 0;
 
       GLfloat dst_mapping_width =
           static_cast<GLfloat>(src_real_width) * dst_width / src_width;
       GLfloat dst_mapping_height =
           static_cast<GLfloat>(src_real_height) * dst_height / src_height;
       GLfloat dst_mapping_xoffset =
           static_cast<GLfloat>(xoffset) * dst_width / src_width;
       GLfloat dst_mapping_yoffset =
           static_cast<GLfloat>(yoffset) * dst_height / src_height;
 
@@ skipping 10797 matching lines @@
 }
 
 // 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 "base/macros.h"
 #include "gpu/command_buffer/service/gles2_cmd_decoder_autogen.h"
 
 }  // namespace gles2
 }  // namespace gpu