mac: Make dynamic DPI changes work.

mac: Make dynamic DPI changes work.

This fixes the software case completely, and makes everything
look good on the hardware path after a few frames. In the
hardware path, the IOSurfaces aren't tagged with their own DPI,
so they are rendered at the wrong scale for a few frames, until
the "DPI changed" message made it from the browser to the
renderer.

This CL adds three things that happen in response to DPI changes:
1.) It reallocates the browser-side BackingStoreMac at the new DPI.
2.) It lets the renderer do a full repaint after DPI changed.
3.) It passes the new DPI on to WebKit (in render_view_impl.cc)

(3) won't have an effect for hardware pages until
https://bugs.webkit.org/show_bug.cgi?id=88916 lands.

BUG=128267
TEST=change from lodpi and hidpi and back, check that software- and
hardware-rendered pages look good after the change in both foreground
and background tabs.

Committed: https://src.chromium.org/viewvc/chrome?view=rev&revision=142099

[Avi (use Gerrit), 2012-06-14 04:51:20]

lgtm

https://chromiumcodereview.appspot.com/10548026/diff/12003/content/browser/re...
File content/browser/renderer_host/render_widget_host_view_mac.mm (right):

https://chromiumcodereview.appspot.com/10548026/diff/12003/content/browser/re...
content/browser/renderer_host/render_widget_host_view_mac.mm:1920: // active, in
DidBecomeSelected().
Not for this CL, but we should rename that to DidBecomeActive...

[Nico, 2012-06-14 04:57:45]

Thanks!

https://chromiumcodereview.appspot.com/10548026/diff/12003/content/browser/re...
File content/browser/renderer_host/render_widget_host_view_mac.mm (right):

https://chromiumcodereview.appspot.com/10548026/diff/12003/content/browser/re...
content/browser/renderer_host/render_widget_host_view_mac.mm:1920: // active, in
DidBecomeSelected().
On 2012/06/14 04:51:20, Avi wrote:
> Not for this CL, but we should rename that to DidBecomeActive...

There's also a mac-only SetActive(true) call :-) That's for painting controls as
active / inactive (think main window vs bg window), while DidBecomeSelected()
marks the active tab on a window.

[commit-bot: I haz the power, 2012-06-14 04:58:01]

CQ is trying da patch. Follow status at
https://chromium-status.appspot.com/cq/thakis@chromium.org/10548026/12003

[Avi (use Gerrit), 2012-06-14 05:08:35]

I just renamed Browser::GetSelectedWebContents to GetActiveWebContents, so some
clarification might be useful here (what does "selected" mean?)
DidBecomeSelected() really means more like "DidBecomeShown"...