Use consistent background color for WKWebViews.

Use consistent background color for WKWebViews.

UIWebViews have their own default background color, while WKWebViews
will interpolate between white and the WKWebView's |-backgroundColor|
while the content is being zoomed.  An earlier solution to this problem
was to use UIWebView's background color behind web views, but this CL
consolidates the backgroundColors for all WKWebViews.

BUG=none

[kkhorimoto, 2016-02-09 23:50:27]

kkhorimoto@chromium.org changed reviewers:
+ gchatz@chromium.org, stuartmorgan@chromium.org

[kkhorimoto, 2016-02-09 23:50:27]

I noticed this while investigating scroll fixes.  The main web views for the app
used white with 0.2 brightness as the WKWebView's backgroundColor, while
interstitials used the color from UIWebView's scroll view's background.

[gchatz, 2016-02-10 01:55:26]

On 2016/02/09 23:50:27, kkhorimoto_ wrote:
> I noticed this while investigating scroll fixes.  The main web views for the
app
> used white with 0.2 brightness as the WKWebView's backgroundColor, while
> interstitials used the color from UIWebView's scroll view's background.

Would this background show up when a transientContentView is visible (and thus
the WebViewContentView is not)?

[kkhorimoto, 2016-02-10 02:18:40]

On 2016/02/10 01:55:26, gchatz wrote:
> On 2016/02/09 23:50:27, kkhorimoto_ wrote:
> > I noticed this while investigating scroll fixes.  The main web views for the
> app
> > used white with 0.2 brightness as the WKWebView's backgroundColor, while
> > interstitials used the color from UIWebView's scroll view's background.
> 
> Would this background show up when a transientContentView is visible (and thus
> the WebViewContentView is not)?

If you're referring to interstitials, then yes (they are backed by WKWebViews
and displayed via CRWWebViewContentViews).  It's possible that other native
content views would have a transparent background, but that's by design.

[kkhorimoto, 2016-02-10 02:20:10]

On 2016/02/10 02:18:40, kkhorimoto_ wrote:
> On 2016/02/10 01:55:26, gchatz wrote:
> > On 2016/02/09 23:50:27, kkhorimoto_ wrote:
> > > I noticed this while investigating scroll fixes.  The main web views for
the
> > app
> > > used white with 0.2 brightness as the WKWebView's backgroundColor, while
> > > interstitials used the color from UIWebView's scroll view's background.
> > 
> > Would this background show up when a transientContentView is visible (and
thus
> > the WebViewContentView is not)?
> 
> If you're referring to interstitials, then yes (they are backed by WKWebViews
> and displayed via CRWWebViewContentViews).  It's possible that other native
> content views would have a transparent background, but that's by design.

I also verified that the bug you fixed when introducing the background color no
longer repros.

[gchatz, 2016-02-10 02:20:14]

On 2016/02/10 02:18:40, kkhorimoto_ wrote:
> On 2016/02/10 01:55:26, gchatz wrote:
> > On 2016/02/09 23:50:27, kkhorimoto_ wrote:
> > > I noticed this while investigating scroll fixes.  The main web views for
the
> > app
> > > used white with 0.2 brightness as the WKWebView's backgroundColor, while
> > > interstitials used the color from UIWebView's scroll view's background.
> > 
> > Would this background show up when a transientContentView is visible (and
thus
> > the WebViewContentView is not)?
> 
> If you're referring to interstitials, then yes (they are backed by WKWebViews
> and displayed via CRWWebViewContentViews).  It's possible that other native
> content views would have a transparent background, but that's by design.

thanks! lgtm

[stuartmorgan, 2016-02-11 17:04:34]

https://codereview.chromium.org/1682273002/diff/20001/ios/web/web_state/ui/cr...
File ios/web/web_state/ui/crw_web_view_content_view.mm (left):

https://codereview.chromium.org/1682273002/diff/20001/ios/web/web_state/ui/cr...
ios/web/web_state/ui/crw_web_view_content_view.mm:78: self.backgroundColor =
[UIColor colorWithRed:kBackgroundRGBComponents[0]
Why don't we still need a background color on the content view; are there not
cases where the web view draws what's behind it, rather than itself?

[kkhorimoto, 2016-02-11 18:27:24]

https://codereview.chromium.org/1682273002/diff/20001/ios/web/web_state/ui/cr...
File ios/web/web_state/ui/crw_web_view_content_view.mm (left):

https://codereview.chromium.org/1682273002/diff/20001/ios/web/web_state/ui/cr...
ios/web/web_state/ui/crw_web_view_content_view.mm:78: self.backgroundColor =
[UIColor colorWithRed:kBackgroundRGBComponents[0]
On 2016/02/11 17:04:34, stuartmorgan wrote:
> Why don't we still need a background color on the content view; are there not
> cases where the web view draws what's behind it, rather than itself?

I'm not sure what you mean about the web view drawing what's behind it rather
than itself.  AFAICT, all web rendering occurs in WKContentView, which is one of
the subviews of WKWebView's scroll view.  So if a page is attempting to render a
semi-transparent element, the subview in WKContentView would be transparent, but
the WKWebView's background color will remain constant in the background.  After
inspecting WKWebView's source, it doesn't look like the background color is ever
updated outside of the public UIView API.  It's only the scroll view whose
backgroundColor changes, but since that's a subview of the WKWebView, it should
never show what's behind.

[stuartmorgan, 2016-02-11 18:39:41]

Makes sense; lgtm

[kkhorimoto, 2016-02-11 19:07:55]

The CQ bit was checked by kkhorimoto@chromium.org

[commit-bot: I haz the power, 2016-02-11 19:09:30]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1682273002/20001
View timeline at
 https://chromium-cq-status.appspot.com/patch-timeline/1682273002/20001

[commit-bot: I haz the power, 2016-02-11 19:16:15]

The CQ bit was unchecked by commit-bot@chromium.org

[commit-bot: I haz the power, 2016-02-11 19:16:16]

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