Credential Manager: Migrate to WebView client-based approach.

Credential Manager: Migrate to WebView client-based approach.

In [1], jam@ suggested that we change the current approach of delivering
the core credential manager implementation via a Platform API piped
through //content. Instead, he proposed creating a client interface, and
setting that directly on the WebView from ChromeContentRendererClient.
This bypasses //content entirely, and makes the Chromium-side
implementation cleaner.

The Blink-side implementation gets a bit messier. In order to ensure
that credential manager doesn't introduce changes to core, this patch
introduces a new client interface in the module, and supplements Page
in order to make this interface available to the module's bindings code.
This is similar to the approach PrerendererClient has taken.

[1]: https://codereview.chromium.org/464883002/#msg9

BUG=400674
Committed: https://src.chromium.org/viewvc/blink?view=rev&revision=180648

[Mike West, 2014-08-20 10:09:53]

pfeldman: Do you have some time this morning to review a platform change? I hope
the CL description gives a reasonable overview of the rationale for the change.

tkent: FYI (as I assume you're nowhere near a computer right now :) ). This
didn't end up being as ugly to implement in Blink as I thought it would be when
we discussed it earlier.

[pfeldman, 2014-08-20 12:23:29]

lgtm

[pfeldman, 2014-08-20 12:23:43]

https://codereview.chromium.org/488993003/diff/20001/public/platform/WebCrede...
File public/platform/WebCredentialManagerClient.h (right):

https://codereview.chromium.org/488993003/diff/20001/public/platform/WebCrede...
public/platform/WebCredentialManagerClient.h:27: virtual void
dispatchFailedSignIn(const WebCredential&, NotificationCallbacks*) = 0;
Do you plan on further growing this interface? If yes, define stub { }
implementations and it will make two-sided patches easier to land.

[Mike West, 2014-08-20 13:05:44]

Thanks!

https://codereview.chromium.org/488993003/diff/20001/public/platform/WebCrede...
File public/platform/WebCredentialManagerClient.h (right):

https://codereview.chromium.org/488993003/diff/20001/public/platform/WebCrede...
public/platform/WebCredentialManagerClient.h:27: virtual void
dispatchFailedSignIn(const WebCredential&, NotificationCallbacks*) = 0;
On 2014/08/20 12:23:43, pfeldman wrote:
> Do you plan on further growing this interface? If yes, define stub { }
> implementations and it will make two-sided patches easier to land.

Sounds reasonable. It's not yet clear what the API will end up looking like;
once it's locked down, we can make this a pure interface again.

[Mike West, 2014-08-20 13:05:52]

The CQ bit was checked by mkwst@chromium.org

[commit-bot: I haz the power, 2014-08-20 13:06:44]

CQ is trying da patch. Follow status at
 https://chromium-status.appspot.com/cq/mkwst@chromium.org/488993003/40001

[commit-bot: I haz the power, 2014-08-20 14:06:49]

Committed patchset #2 (40001) as 180648