Use CheckedNumeric when converting SkIRect to gfx::Rect.

ui/gfx/skia_util.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 "ui/gfx/skia_util.h"
 
 #include <stddef.h>
 #include <stdint.h>
 
 #include "base/numerics/safe_conversions.h"
+#include "base/numerics/safe_math.h"
 #include "third_party/skia/include/core/SkBitmap.h"
 #include "third_party/skia/include/core/SkColorFilter.h"
 #include "third_party/skia/include/core/SkColorPriv.h"
 #include "third_party/skia/include/core/SkUnPreMultiply.h"
 #include "third_party/skia/include/effects/SkBlurMaskFilter.h"
 #include "third_party/skia/include/effects/SkGradientShader.h"
 #include "third_party/skia/include/effects/SkLayerDrawLooper.h"
 #include "ui/gfx/geometry/quad_f.h"
 #include "ui/gfx/geometry/rect.h"
 #include "ui/gfx/geometry/rect_f.h"
@@ skipping 19 matching lines @@
   return SkRect::MakeXYWH(
       SkIntToScalar(rect.x()), SkIntToScalar(rect.y()),
       SkIntToScalar(rect.width()), SkIntToScalar(rect.height()));
 }
 
 SkIRect RectToSkIRect(const Rect& rect) {
   return SkIRect::MakeXYWH(rect.x(), rect.y(), rect.width(), rect.height());
 }
 
 Rect SkIRectToRect(const SkIRect& rect) {
-  return Rect(rect.x(), rect.y(), rect.width(), rect.height());
+  return Rect(rect.x(), rect.y(),
+              (base::CheckedNumeric<int>(rect.right()) - rect.left())

[danakj, 2016/08/22 20:01:49]

I see, ok so checking right-left here makes sense then.

+                  .ValueOrDefault(std::numeric_limits<int>::max()),

[danakj, 2016/08/22 20:01:49]

But if x >= 0, the right() will still overflow with a width of max() so we need
some clamping in gfx::Rect too?

[jbroman, 2016/08/23 03:26:58]

That cannot happen here, since SkIRect::fRight must have been in the range of
int32_t, and we do not support any platforms where sizeof(int) <
sizeof(int32_t).

The only exception I can think of is the case of a rectangle with negative
width/height in Skia, which could underflow. I'll handle that case and add unit
tests to clarify.

+              (base::CheckedNumeric<int>(rect.bottom()) - rect.top())
+                  .ValueOrDefault(std::numeric_limits<int>::max()));
 }
 
 SkRect RectFToSkRect(const RectF& rect) {
   return SkRect::MakeXYWH(SkFloatToScalar(rect.x()),
                           SkFloatToScalar(rect.y()),
                           SkFloatToScalar(rect.width()),
                           SkFloatToScalar(rect.height()));
 }
 
 RectF SkRectToRectF(const SkRect& rect) {
@@ skipping 215 matching lines @@
   static const SkScalar kSkToHbRatio = SK_Scalar1 / kHbUnit1;
   return kSkToHbRatio * value;
 }
 
 float HarfBuzzUnitsToFloat(int value) {
   static const float kFloatToHbRatio = 1.0f / kHbUnit1;
   return kFloatToHbRatio * value;
 }
 
 }  // namespace gfx