Remove dependency of AsyncResourceLoader on content/browser/host_zoom_map_impl.h

Remove dependency of AsyncResourceLoader on c/b/host_zoom_map_impl.h

This is accomplished by adding a ResourceDispatcherHostDelegate wrapper
around the existing delegate that allows delegation from network back to
content to do the content-specific functionality, before then delegating
onwards to the existing content client (chrome). This new class is
called ContentResourceDispatcherHostDelegate.

Additionally, to be able to install the
ContentResourceDispatcherHostDelegate, there's a
ContentResourceDispatcherHost that wraps ResourceDispatcherHostImpl so
that SetDelegate can wrap the new delegate around the existing one.

After all that boilerplate, we can move the use of
content/browser/host_zoom_map_impl.cc|h to
ContentResourceDispatcherHostDelegate to avoid having c/b/loader use it
in OnRequestStarted().

R=jam@chromium.org
BUG=609607, 598073

[scottmg, 2016-05-06 21:03:00]

Description was changed from

==========
Remove dependency of AsyncResourceLoader on content/browser/host_zoom_map_impl.h

R=jam@chromium.org
BUG=609607,598073
==========

to

==========
Remove dependency of AsyncResourceLoader on c/b/host_zoom_map_impl.h

This is accomplished by adding a ResourceDispatcherHostDelegate wrapper
around the existing delegate that allows delegation from network back to
content to do the content-specific functionality, before then delegating
onwards to the existing content client (chrome). This new class is
called ContentResourceDispatcherHostDelegate.

Additionally, to be able to install the
ContentResourceDispatcherHostDelegate, there's a
ContentResourceDispatcherHost that wraps ResourceDispatcherHostImpl so
that SetDelegate can wrap the new delegate around the existing one.

After all that boilerplate, we can move the use of
content/browser/host_zoom_map_impl.cc|h to
ContentResourceDispatcherHostDelegate to avoid having c/b/loader use it
in OnRequestStarted().

R=jam@chromium.org
BUG=609607,598073
==========

[scottmg, 2016-05-06 21:52:15]

Not sure if this is too complicated for what it's accomplishing. wdyt?

https://codereview.chromium.org/1960743002/diff/1/content/browser/content_res...
File content/browser/content_resource_dispatcher_host_delegate.cc (right):

https://codereview.chromium.org/1960743002/diff/1/content/browser/content_res...
content/browser/content_resource_dispatcher_host_delegate.cc:108: const
ResourceRequestInfoImpl* info =
Moving this block of code out of AsyncResourceHandler is the point of this
change.

[scottmg, 2016-06-15 17:02:18]

closing as we're going another way (making the async mojo interface directly)