[Android WebView] Fix WideViewport use case after r157293

[Android WebView] Fix WideViewport use case after r157293

This fixes Chromium test AwSettingsTest.testUseWideViewportLayoutWidth

BUG=285995
Committed: https://src.chromium.org/viewvc/blink?view=rev&revision=157386

[mnaganov (inactive), 2013-09-06 00:24:05]

Hello Rune,

It seems, we were missing an important test case in WebFrameTests, so we only
caught the regression upstream in Chromium.

I'm not quite sure what "ExtendToZoom" means, but it looks like it's not what we
are getting in the case when the page doesn't have a viewport tag.

[rune, 2013-09-06 08:19:49]

On 2013/09/06 00:24:05, Mikhail Naganov (Chromium) wrote:
> Hello Rune,
> 
> It seems, we were missing an important test case in WebFrameTests, so we only
> caught the regression upstream in Chromium.
> 
> I'm not quite sure what "ExtendToZoom" means, but it looks like it's not what
we
> are getting in the case when the page doesn't have a viewport tag.

It's the extend-to-zoom keyword from the css-device-adapt spec:

http://dev.w3.org/csswg/css-device-adapt/#lsquoextend-to-zoomrsquo

That section has an explanation. In short, for meta viewport, when the
constrained scale value is such that the constrained width will not fill the
window width at that scale value, the constrained width is extended to fill the
window.

For @viewport we've decided to not let the scale (zoom) affect viewport
width/height constraining. Thus, making it necessary to have an internal
extend-to-zoom value to have backwards compatibility with the meta viewport
implementations.

My changes introduced "@viewport { min-width: 980px }" in the UA stylesheet
which means the max-width is 'auto'. This is where the 'auto' value comes from
when no meta viewport tag is present. If you look at the css-device-adapt spec,
there is also another case where the max-width is 'auto', and that is if the
meta tag has no width, but has a height property. In that case max-width will be
'auto' and not 'extend-to-zoom'. That case is also handled by your fix, and
correctly so. There should probably be a WebFrameTest for that as well
(useWideViewport=false + <meta name="viewport" content="height=1000"> ?).

I think the intention of the useWideViewport setting can be described as a UA
@viewport as:

useWideViewport=true: @viewport { min-width: 980px }
useWideViewport=false: @viewport {}

But there is quirkiness with for instance the check for zoom != 1 in the current
code which means that this isn't entirely correct for backwards compatibility.

[rune, 2013-09-06 08:20:58]

In short, LGTM with an added WebFrameTest for: useWideViewport=false + <meta
name="viewport" content="height=1000">

[rune, 2013-09-06 08:22:27]

@mnaganov: Thanks a lot for handling this issue caused by me, and sorry for the
trouble :-)

[mnaganov (inactive), 2013-09-06 18:12:45]

Rune, thanks for the suggestion! Added the test.

Adam, can you please take a look?

[abarth-chromium, 2013-09-06 19:23:50]

lgtm

[commit-bot: I haz the power, 2013-09-06 19:24:11]

CQ is trying da patch. Follow status at
https://chromium-status.appspot.com/cq/mnaganov@chromium.org/23459006/7001

[commit-bot: I haz the power, 2013-09-06 20:56:02]

Change committed as 157386