Document calls to the "rules for updating the text track rendering"

Document calls to the "rules for updating the text track rendering"

Per spec there are only two calls to these rules:
 * The last step of the "time marches on" algorithm.
 * "When the user agent starts exposing a user interface for a video
   element."

We have the first call, and two others that are needed when the text
track mode changes between hidden and visible. A spec bug was filed
for this case: https://www.w3.org/Bugs/Public/show_bug.cgi?id=28236

BUG=322434
NOTRY=true

Committed: https://src.chromium.org/viewvc/blink?view=rev&revision=192148

[philipj_slow, 2015-03-19 06:18:59]

philipj@opera.com changed reviewers:
+ fs@opera.com

[philipj_slow, 2015-03-19 06:19:00]

PTAL

[philipj_slow, 2015-03-19 06:46:26]

realize fault; lower ambitions

[philipj_slow, 2015-03-19 06:47:52]

OK, so there actually wasn't much cleanup possible here without breaking things,
but hopefully documenting what I learned will help future readers.

This m_processingPreferenceChange bit is rather unsightly, but I haven't looked
into what it would take to remove it.

[fs, 2015-03-19 09:50:33]

LGTM w/ comment

https://codereview.chromium.org/1022743002/diff/20001/Source/core/html/HTMLMe...
File Source/core/html/HTMLMediaElement.cpp (right):

https://codereview.chromium.org/1022743002/diff/20001/Source/core/html/HTMLMe...
Source/core/html/HTMLMediaElement.cpp:3361: if (assumption ==
AssumeVisibleChange)
I'm not really 100% convinced that this call should be predicated like this -
but I'm not quite sure what the |assumption| is expected to achieve either (I
think I'd rather drop it.)

[philipj_slow, 2015-03-19 10:04:54]

https://codereview.chromium.org/1022743002/diff/20001/Source/core/html/HTMLMe...
File Source/core/html/HTMLMediaElement.cpp (right):

https://codereview.chromium.org/1022743002/diff/20001/Source/core/html/HTMLMe...
Source/core/html/HTMLMediaElement.cpp:3361: if (assumption ==
AssumeVisibleChange)
On 2015/03/19 09:50:33, fs wrote:
> I'm not really 100% convinced that this call should be predicated like this -
> but I'm not quite sure what the |assumption| is expected to achieve either (I
> think I'd rather drop it.)

To play it safe I can make it unconditional again, making this CL documentation
only.

I'd also be happy to see VisibilityChangeAssumption (and RemovalNotification and
many flags of this sort) gone, but it would take some history digging to
understand what the point is.

[philipj_slow, 2015-03-19 10:06:55]

leave comments only

[philipj_slow, 2015-03-19 10:09:12]

The CQ bit was checked by philipj@opera.com

[philipj_slow, 2015-03-19 10:09:13]

The patchset sent to the CQ was uploaded after l-g-t-m from fs@opera.com
Link to the patchset: https://codereview.chromium.org/1022743002/#ps40001
(title: "leave comments only")

[commit-bot: I haz the power, 2015-03-19 10:09:29]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1022743002/40001

[commit-bot: I haz the power, 2015-03-19 10:10:02]

Committed patchset #3 (id:40001) as
https://src.chromium.org/viewvc/blink?view=rev&revision=192148