Type conversion fixes, ui/gfx/ edition.

ui/gfx/animation/tween.cc

Index: ui/gfx/animation/tween.cc
diff --git a/ui/gfx/animation/tween.cc b/ui/gfx/animation/tween.cc
index 483d772b5b4d47f4f7ba7f65d391f665df5819db..c05c3c38fb67c2d817887b0f0a52173e8363856c 100644
--- a/ui/gfx/animation/tween.cc
+++ b/ui/gfx/animation/tween.cc
@@ -14,6 +14,7 @@
 
 #include "base/basictypes.h"
 #include "base/logging.h"
+#include "base/numerics/safe_conversions.h"
 #include "ui/gfx/geometry/cubic_bezier.h"
 #include "ui/gfx/safe_integer_conversions.h"
 
@@ -71,7 +72,7 @@ double Tween::CalculateValue(Tween::Type type, double state) {
 
 namespace {
 uint8 FloatToColorByte(float f) {
-  return std::min(std::max(ToRoundedInt(f * 255.f), 0), 255);
+  return base::saturated_cast<uint8>(ToRoundedInt(f * 255.f));
 }
 
 uint8 BlendColorComponents(uint8 start,
@@ -149,7 +150,7 @@ int Tween::IntValueBetween(double value, int start, int target) {
 
 //static
 int Tween::LinearIntValueBetween(double value, int start, int target) {
-  return std::floor(0.5 + DoubleValueBetween(value, start, target));
+  return ToRoundedInt(DoubleValueBetween(value, start, target));

[Peter Kasting, 2014/10/21 00:53:56]

Note: This causes test failures in TweenTest.LinearIntValueBetweenNegative
because the rounding behavior is changed in my patch from "round toward positive
infinity" to "round away from 0".  "Round away from 0" matches e.g. std::round()
and seems more intuitive to me, so I'm inclined to change the test expectations,
but let me know what you think should be done.

[danakj, 2014/10/23 15:20:42]

We should have ajuma decide the right thing here, it may be speced.

[ajuma, 2014/10/23 15:44:39]

Rounding towards positive infinity is indeed part of the CSS transitions spec.
See http://www.w3.org/TR/css3-transitions/#animatable-types

[Peter Kasting, 2014/10/23 17:29:45]

This isn't used for CSS transitions, though.  This is only used in Chrome UI
animations.  How does the CSS spec relate?

(Also, if we have a ToRoundedInt() in ui/gfx/ at all, and it rounds away from
zero, aren't we already risking other people rounding in this way?  Are you guys
proposing changing how that method is implemented?)

[ajuma, 2014/10/23 17:37:11]

It's used by cc::FilterOperation when animating CSS filters.

[Peter Kasting, 2014/10/23 17:39:52]

I see...

I'll change this; in the future it would be awesome if we could add comments
documenting subtle things like how this piece of ui/ is actually used for web
content, and that there's a spec that controls its behavior.  (I'll add such a
comment here.)

[ajuma, 2014/10/23 17:42:14]

FWIW, the .h file has such a comment :)  But it's true that having a comment
beside the implementation would help to avoid future confusion.

[danakj, 2014/10/23 17:43:23]

I'm not proposing that. ToRoundedInt should work like round(). But in this case
round() is not the right behaviour due to spec.

 }
 
 // static