Normalize top controls offset to (0, 1), Chromium-side.

Normalize top controls offset to (0, 1), Chromium-side.

Since top controls height can now be changed, storing top controls
offset as an absolute value causes problems.  Normalizing its format to
(0, 1) means we we don't need to adjust it when the height changes.  It
also improves readability and means TopControlsManager will compute
correctly even when the height is currently 0.

This patch also switches top controls to use SyncedProperty.

See also Blink-side patch: https://codereview.chromium.org/882683003

BUG=430635
Committed: https://crrev.com/6004fe0188ac900b02b843a9bff3ad8e569d616a
Cr-Commit-Position: refs/heads/master@{#315216}

[aelias_OOO_until_Jul13, 2015-02-05 06:14:12]

aelias@chromium.org changed reviewers:
+ bokan@chromium.org, dtrainor@chromium.org

[aelias_OOO_until_Jul13, 2015-02-05 06:16:15]

Hi bokan@ and dtrainor@, PTAL.

[Changwan Ryu, 2015-02-06 01:22:12]

On 2015/02/05 06:16:15, aelias wrote:
> Hi bokan@ and dtrainor@, PTAL.

Great job! I've verified that this fixes the original problem I suggested.

Could you also add unit tests, something like
https://codereview.chromium.org/886763004/diff/20001/cc/input/top_controls_ma...
as that behavior was previously broken?

[aelias_OOO_until_Jul13, 2015-02-06 01:43:29]

On 2015/02/06 at 01:22:12, changwan wrote:
> Great job! I've verified that this fixes the original problem I suggested.
> 
> Could you also add unit tests, something like
https://codereview.chromium.org/886763004/diff/20001/cc/input/top_controls_ma...
> as that behavior was previously broken?

Done, I added that unit test almost verbatim.

[David Trainor- moved to gerrit, 2015-02-06 18:48:01]

lgtm

Awesome thanks for doing this! :)

https://chromiumcodereview.appspot.com/901813002/diff/1/cc/input/top_controls...
File cc/input/top_controls_manager.cc (left):

https://chromiumcodereview.appspot.com/901813002/diff/1/cc/input/top_controls...
cc/input/top_controls_manager.cc:198: if (direction == SHOWING_CONTROLS &&
client_->ControlsTopOffset() == 0)
No more early outs if we don't have to animate?

https://chromiumcodereview.appspot.com/901813002/diff/1/cc/input/top_controls...
File cc/input/top_controls_manager.cc (right):

https://chromiumcodereview.appspot.com/901813002/diff/1/cc/input/top_controls...
cc/input/top_controls_manager.cc:100: controls_scroll_begin_offset_ =
ContentTopOffset();
So you're changing what this means to be content offset instead of top controls
offset to make ti easier to just compute the ratio below?  Just checking to make
sure I understand this part.

[aelias_OOO_until_Jul13, 2015-02-06 20:02:06]

New patchsets have been uploaded after l-g-t-m from dtrainor@chromium.org

[aelias_OOO_until_Jul13, 2015-02-06 20:28:19]

aelias@chromium.org changed reviewers:
+ sievers@chromium.org

[aelias_OOO_until_Jul13, 2015-02-06 20:28:29]

Adding sievers@ for content/ OWNERS.

https://codereview.chromium.org/901813002/diff/1/cc/input/top_controls_manage...
File cc/input/top_controls_manager.cc (left):

https://codereview.chromium.org/901813002/diff/1/cc/input/top_controls_manage...
cc/input/top_controls_manager.cc:198: if (direction == SHOWING_CONTROLS &&
client_->ControlsTopOffset() == 0)
On 2015/02/06 18:48:01, David Trainor wrote:
> No more early outs if we don't have to animate?

No, there are enough early outs elsewhere and this is a private method, so these
early outs were dead code.

Come to think of it, in this situation we usually replace with DCHECKs instead
of deleting the lines completely, so I added some DCHECKs here in the latest
patch set.

https://codereview.chromium.org/901813002/diff/1/cc/input/top_controls_manage...
File cc/input/top_controls_manager.cc (right):

https://codereview.chromium.org/901813002/diff/1/cc/input/top_controls_manage...
cc/input/top_controls_manager.cc:100: controls_scroll_begin_offset_ =
ContentTopOffset();
On 2015/02/06 18:48:01, David Trainor wrote:
> So you're changing what this means to be content offset instead of top
controls
> offset to make ti easier to just compute the ratio below?  Just checking to
make
> sure I understand this part.

Right, it simplifies the math to compute SetCurrentTopControlsShownRatio below
-- I don't have to add 1 there.  In general, I switched everything in this file
away from using ControlsTopOffset because I find it confusing to work with (it's
weird to have something that's never a positive number).

[no sievers, 2015-02-06 21:03:47]

On 2015/02/06 20:28:29, aelias wrote:
> Adding sievers@ for content/ OWNERS.
>

lgtm

[aelias_OOO_until_Jul13, 2015-02-07 20:27:06]

The CQ bit was checked by aelias@chromium.org

[commit-bot: I haz the power, 2015-02-07 20:27:49]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/901813002/60001

[aelias_OOO_until_Jul13, 2015-02-07 20:36:04]

The CQ bit was unchecked by aelias@chromium.org

[aelias_OOO_until_Jul13, 2015-02-07 20:46:16]

New patchsets have been uploaded after l-g-t-m from sievers@chromium.org

[aelias_OOO_until_Jul13, 2015-02-07 21:28:53]

The CQ bit was checked by aelias@chromium.org

[commit-bot: I haz the power, 2015-02-07 21:29:14]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/901813002/80001

[commit-bot: I haz the power, 2015-02-07 21:43:08]

Committed patchset #5 (id:80001)

[commit-bot: I haz the power, 2015-02-07 21:43:41]

Patchset 5 (id:??) landed as
https://crrev.com/6004fe0188ac900b02b843a9bff3ad8e569d616a
Cr-Commit-Position: refs/heads/master@{#315216}