Add non-member non-mutating methods for common gfx::Rect operations.

Add non-member non-mutating methods for common gfx::Rect operations.

This adds non-member methods that return a new Rect (or RectF) object
as their result instead of mutating an existing rect. We add:

Rect gfx::IntersectRects(Rect, Rect)
RectF gfx::IntersectRects(RectF, RectF)
Rect gfx::UnionRects(Rect, Rect)
RectF gfx::UnionRects(RectF, RectF)
Rect gfx::SubtractRects(Rect, Rect)
RectF gfx::SubtractRects(RectF, RectF)
RectF gfx::ScaleRect(RectF, scale)
RectF gfx::ScaleRect(RectF, x_scale, y_scale)

In CL https://codereview.chromium.org/11110004/ we made all
member methods of Rect (and RectF) mutate the existing
object, so these methods are added for cases where we want
the result to create a new object instead.

BUG=147395
R=sky

Committed: https://src.chromium.org/viewvc/chrome?view=rev&revision=164760

[danakj, 2012-10-25 18:31:19]

These new methods are similar to
https://dev.mobileread.com/trac/webkitbrowser/browser/trunk/WebKit-r30377/Web...

I have added the same methods found in WebKit, but also added Subtraction() as
it was a case hit a number of times.

I left out ClampToCenteredRect and AdjustToFit, as they are not used as often in
situations like this, and they are less well-defined/commonly-understood
operations in general.

[danakj, 2012-10-25 18:33:29]

I went through https://codereview.chromium.org/11110004/ and looked at each case
modified there, and switched them over to these new methods where it made sense,
and left them alone where the other methods were more clear/concise.

[sky, 2012-10-25 23:31:52]

https://codereview.chromium.org/11270042/diff/1/ui/gfx/rect.h
File ui/gfx/rect.h (right):

https://codereview.chromium.org/11270042/diff/1/ui/gfx/rect.h#newcode78
ui/gfx/rect.h:78: inline Rect Intersection(const Rect& a, const Rect& b) {
I think we need more descriptive names otherwise we can easily conflict. Maybe
IntersectRects. Is there a compelling reason to inline these?

[danakj, 2012-10-26 00:16:04]

https://codereview.chromium.org/11270042/diff/1/ui/gfx/rect.h
File ui/gfx/rect.h (right):

https://codereview.chromium.org/11270042/diff/1/ui/gfx/rect.h#newcode78
ui/gfx/rect.h:78: inline Rect Intersection(const Rect& a, const Rect& b) {
On 2012/10/25 23:31:53, sky wrote:
> I think we need more descriptive names otherwise we can easily conflict. Maybe
> IntersectRects.

Sure, though I thought the same and enne@ convinced me otherwise. Rect does not
implicitly convert to/from anything else, so what would we conflict with?

> Is there a compelling reason to inline these?

Nope, other than they are small. Will move to the .cc.

[danakj, 2012-10-26 00:24:26]

Made non-inline and renamed to IntersectRects, ScaleRect, etc.

[sky, 2012-10-26 19:38:44]

LGTM

[danakj, 2012-10-26 19:52:42]

Need some OWNERS review:

+jamesr for cc/ webkit/ content/renderer/
+piman for content/common/gpu and webkit/plugins/ppapi

[jamesr, 2012-10-26 19:59:36]

lgtm

[Ken Russell (switch to Gerrit), 2012-10-27 01:16:18]

content/common/gpu LGTM

[piman, 2012-10-29 17:12:00]

lgtm

lgtm

[piman, 2012-10-29 17:12:00]

lgtm