Add a Physical Web omnibox autocomplete provider

components/omnibox/browser/autocomplete_provider_client.h

Index: components/omnibox/browser/autocomplete_provider_client.h
diff --git a/components/omnibox/browser/autocomplete_provider_client.h b/components/omnibox/browser/autocomplete_provider_client.h
index 80211f51a2f5b89c21a524b8fcfc3122a23a13ed..5c2e47433f76b1eb0a4f19cdfdf9ecae62d99ebc 100644
--- a/components/omnibox/browser/autocomplete_provider_client.h
+++ b/components/omnibox/browser/autocomplete_provider_client.h
@@ -22,6 +22,7 @@ class AutocompleteSchemeClassifier;
 class GURL;
 class InMemoryURLIndex;
 class KeywordProvider;
+class PhysicalWebDataSource;
 class PrefService;
 class ShortcutsBackend;
 
@@ -61,6 +62,7 @@ class AutocompleteProviderClient {
   virtual scoped_refptr<ShortcutsBackend> GetShortcutsBackendIfExists() = 0;
   virtual std::unique_ptr<KeywordExtensionsDelegate>
   GetKeywordExtensionsDelegate(KeywordProvider* keyword_provider) = 0;
+  virtual PhysicalWebDataSource* GetPhysicalWebDataSource() = 0;

[Mark P, 2016/08/08 20:41:37]

I think there's a lot of stuff here already but I must ask: is there a way you
can get the physical web data source to the provider without adding more here. 
For instance, can you simply pass it in as part of the constructor in
autocomplete_controller, no need to muck with this generic
AutocompleteProviderClient?

[mattreynolds, 2016/08/09 21:42:02]

The issue is that the PhysicalWebDataSource instance is owned by
ApplicationContext, which is iOS-specific and can't be accessed directly from
//chrome/browser (or //components/omnibox).  AutocompleteProviderClientImpl
appears to be where we're embedding other iOS-specific implementations of
components needed by autocomplete providers which is why I added it there.  When
we bring the feature to other platforms we'll attach the data source instance to
BrowserProcess and make it accessible to the omnibox component through
ChromeAutocompleteProviderClient::GetPhysicalWebDataSource().

Re: AutocompleteController, it is created by OmniboxController, which is in turn
created by OmniboxEditModel, OmniboxView, and finally OmniboxViewIOS. 
OmniboxViewIOS appears to be the first point in the chain where we can add
iOS-specific embeddings, but doesn't seem like a good fit for the data source
method.  WDYT?

[Mark P, 2016/08/10 23:33:19]

Makes sense to me.  I hadn't rememberad all those iOS overrides in the impl
file.
I agree, passing something the physical web data source down from OmniboxView
seems wrong.

 
   // The value to use for Accept-Languages HTTP header when making an HTTP
   // request.