[Reland] Maintain HostZoom connection per-frame on browser side

[Reland] Maintain HostZoom connection per-frame on browser side

This CL is a reland of https://codereview.chromium.org/2581143002.
That CL was reverted due to a failing layouttest. Investigation revealed
that the layouttest itself was busted, and that test has now been
removed (see the discussion on crbug.com/673065 for details).

Original CL description:

HostZoomMapObserver is a per-WebContents class, while the HostZoom Mojo
connection is per-frame. Before this CL, HostZoomMapObserver was
maintaining one HostZoom connection and rebinding it every time a new
RenderFrame was created. This meant that HostZoomMapObserver was
continually losing connections to existing frames. This CL changes
HostZoomMapObserver to maintain one connection per-RenderFrame in a
map indexed by the corresponding RenderFrameHost.

BUG=673065
TEST=Visit news.ycombinator.com and increase the zoom level to 175%.
Click the top link. Hit back: news.ycombinator.com should still be
zoomed to 175%.

TBR=jochen

Review-Url: https://codereview.chromium.org/2609003004
Cr-Commit-Position: refs/heads/master@{#441629}
(cherry picked from commit e7aa3298381a03045a4a6dc6379990275dbfb247)

Review-Url: https://codereview.chromium.org/2619353005 .
Cr-Commit-Position: refs/branch-heads/2924@{#713}
Cr-Branched-From: 3a87aecc31cd1ffe751dd72c04e5a96a1fc8108a-refs/heads/master@{#433059}
Committed: https://chromium.googlesource.com/chromium/src/+/31fcef32237693e060e1d4286532febfd9627232

[blundell, 2017-01-10 12:43:19]

Description was changed from

==========
[Reland] Maintain HostZoom connection per-frame on browser side

This CL is a reland of https://codereview.chromium.org/2581143002.
That CL was reverted due to a failing layouttest. Investigation revealed
that the layouttest itself was busted, and that test has now been
removed (see the discussion on crbug.com/673065 for details).

Original CL description:

HostZoomMapObserver is a per-WebContents class, while the HostZoom Mojo
connection is per-frame. Before this CL, HostZoomMapObserver was
maintaining one HostZoom connection and rebinding it every time a new
RenderFrame was created. This meant that HostZoomMapObserver was
continually losing connections to existing frames. This CL changes
HostZoomMapObserver to maintain one connection per-RenderFrame in a
map indexed by the corresponding RenderFrameHost.

BUG=673065
TEST=Visit news.ycombinator.com and increase the zoom level to 175%.
Click the top link. Hit back: news.ycombinator.com should still be
zoomed to 175%.

TBR=jochen

Review-Url: https://codereview.chromium.org/2609003004
Cr-Commit-Position: refs/heads/master@{#441629}
(cherry picked from commit e7aa3298381a03045a4a6dc6379990275dbfb247)
==========

to

==========
[Reland] Maintain HostZoom connection per-frame on browser side

This CL is a reland of https://codereview.chromium.org/2581143002.
That CL was reverted due to a failing layouttest. Investigation revealed
that the layouttest itself was busted, and that test has now been
removed (see the discussion on crbug.com/673065 for details).

Original CL description:

HostZoomMapObserver is a per-WebContents class, while the HostZoom Mojo
connection is per-frame. Before this CL, HostZoomMapObserver was
maintaining one HostZoom connection and rebinding it every time a new
RenderFrame was created. This meant that HostZoomMapObserver was
continually losing connections to existing frames. This CL changes
HostZoomMapObserver to maintain one connection per-RenderFrame in a
map indexed by the corresponding RenderFrameHost.

BUG=673065
TEST=Visit news.ycombinator.com and increase the zoom level to 175%.
Click the top link. Hit back: news.ycombinator.com should still be
zoomed to 175%.

TBR=jochen

Review-Url: https://codereview.chromium.org/2609003004
Cr-Commit-Position: refs/heads/master@{#441629}
(cherry picked from commit e7aa3298381a03045a4a6dc6379990275dbfb247)

Review-Url: https://codereview.chromium.org/2619353005 .
Cr-Commit-Position: refs/branch-heads/2924@{#713}
Cr-Branched-From:
3a87aecc31cd1ffe751dd72c04e5a96a1fc8108a-refs/heads/master@{#433059}
Committed:
https://chromium.googlesource.com/chromium/src/+/31fcef32237693e060e1d4286532...
==========

[blundell, 2017-01-10 12:43:20]

Committed patchset #1 (id:1) manually as
31fcef32237693e060e1d4286532febfd9627232.