Added a console warning when <picture><source src></picture> is used.

Added a console warning when <picture><source src></picture> is used.

Following a discussion on the lack of support for <picture><source src></picture> 
that happened on https://github.com/ResponsiveImagesCG/picture-element/issues/224 
I would like to add a console warning to guide authors away from this pattern.

BUG=403260
Committed: https://src.chromium.org/viewvc/blink?view=rev&revision=180187

[Mike West, 2014-08-13 13:57:24]

It might be worth measuring this. LGTM either way.

https://codereview.chromium.org/466353002/diff/40001/Source/core/html/HTMLIma...
File Source/core/html/HTMLImageElement.cpp (right):

https://codereview.chromium.org/466353002/diff/40001/Source/core/html/HTMLIma...
Source/core/html/HTMLImageElement.cpp:287:
document().addConsoleMessage(ConsoleMessage::create(RenderingMessageSource,
WarningMessageLevel, "<source src> with a <picture> parent is invalid and
therefore ignored. Use <source srcset> instead."));
It might be worthwhile to measure how often this occurs to inform future
decisions. You could do that while writing out the message via
UseCounter::countDeprecation.

[Yoav Weiss, 2014-08-13 14:24:56]

On 2014/08/13 13:57:24, Mike West (OOO until 19th) wrote:
> It might be worth measuring this. LGTM either way.
> 
>
https://codereview.chromium.org/466353002/diff/40001/Source/core/html/HTMLIma...
> File Source/core/html/HTMLImageElement.cpp (right):
> 
>
https://codereview.chromium.org/466353002/diff/40001/Source/core/html/HTMLIma...
> Source/core/html/HTMLImageElement.cpp:287:
> document().addConsoleMessage(ConsoleMessage::create(RenderingMessageSource,
> WarningMessageLevel, "<source src> with a <picture> parent is invalid and
> therefore ignored. Use <source srcset> instead."));
> It might be worthwhile to measure how often this occurs to inform future
> decisions. You could do that while writing out the message via
> UseCounter::countDeprecation.

Good idea! :)
I added one, but since I've never added a use counter before, please make sure I
didn't do anything foolish.

Also uploaded a CL with a new histograms.xml that the UseCounter code comments
told me to generate: https://codereview.chromium.org/468173002

[Yoav Weiss, 2014-08-13 14:27:16]

On 2014/08/13 14:24:56, Yoav Weiss wrote:
> On 2014/08/13 13:57:24, Mike West (OOO until 19th) wrote:
> > It might be worth measuring this. LGTM either way.
> > 
> >
>
https://codereview.chromium.org/466353002/diff/40001/Source/core/html/HTMLIma...
> > File Source/core/html/HTMLImageElement.cpp (right):
> > 
> >
>
https://codereview.chromium.org/466353002/diff/40001/Source/core/html/HTMLIma...
> > Source/core/html/HTMLImageElement.cpp:287:
> > document().addConsoleMessage(ConsoleMessage::create(RenderingMessageSource,
> > WarningMessageLevel, "<source src> with a <picture> parent is invalid and
> > therefore ignored. Use <source srcset> instead."));
> > It might be worthwhile to measure how often this occurs to inform future
> > decisions. You could do that while writing out the message via
> > UseCounter::countDeprecation.
> 
> Good idea! :)
> I added one, but since I've never added a use counter before, please make sure
I
> didn't do anything foolish.

Didn't see you're OOO until the 19th. I'll get someone else to take a look.
Thanks! :)

> 
> Also uploaded a CL with a new histograms.xml that the UseCounter code comments
> told me to generate: https://codereview.chromium.org/468173002

[Mike West, 2014-08-13 14:29:31]

https://codereview.chromium.org/466353002/diff/60001/Source/core/html/HTMLIma...
File Source/core/html/HTMLImageElement.cpp (right):

https://codereview.chromium.org/466353002/diff/60001/Source/core/html/HTMLIma...
Source/core/html/HTMLImageElement.cpp:287:
document().addConsoleMessage(ConsoleMessage::create(RenderingMessageSource,
WarningMessageLevel, "<source src> with a <picture> parent is invalid and
therefore ignored. Use <source srcset> instead."));
You can drop this message here, and add it to the deprecation message list in
UseCounter.cpp:
https://code.google.com/p/chromium/codesearch#chromium/src/third_party/WebKit...

[Yoav Weiss, 2014-08-13 14:58:41]

On 2014/08/13 14:29:31, Mike West (OOO until 19th) wrote:
>
https://codereview.chromium.org/466353002/diff/60001/Source/core/html/HTMLIma...
> File Source/core/html/HTMLImageElement.cpp (right):
> 
>
https://codereview.chromium.org/466353002/diff/60001/Source/core/html/HTMLIma...
> Source/core/html/HTMLImageElement.cpp:287:
> document().addConsoleMessage(ConsoleMessage::create(RenderingMessageSource,
> WarningMessageLevel, "<source src> with a <picture> parent is invalid and
> therefore ignored. Use <source srcset> instead."));
> You can drop this message here, and add it to the deprecation message list in
> UseCounter.cpp:
>
https://code.google.com/p/chromium/codesearch#chromium/src/third_party/WebKit...

Added it the right way.
One difference between the two methods is that deprecation warnings don't give
line numbers in which the markup occurred.
Is that by design (to reduce log spam) or a bug?

[Mike West, 2014-08-13 15:01:43]

LGTM.

On 2014/08/13 14:58:41, Yoav Weiss wrote:
> Added it the right way.
> One difference between the two methods is that deprecation warnings don't give
> line numbers in which the markup occurred.
> Is that by design (to reduce log spam) or a bug?

File a bug. :)

[Yoav Weiss, 2014-08-13 15:46:58]

The CQ bit was checked by yoav@yoav.ws

[commit-bot: I haz the power, 2014-08-13 15:48:14]

CQ is trying da patch. Follow status at
 https://chromium-status.appspot.com/cq/yoav@yoav.ws/466353002/80001

[commit-bot: I haz the power, 2014-08-13 16:15:52]

Committed patchset #5 (80001) as 180187