[PhysicalWeb] Add physical_web namespace.

ios/chrome/browser/application_context.h

Index: ios/chrome/browser/application_context.h
diff --git a/ios/chrome/browser/application_context.h b/ios/chrome/browser/application_context.h
index 7d14884d97d308fa50a43ca421ca3596416ae024..311f6b1c02239b0d17a4227541bfb179325b1df3 100644
--- a/ios/chrome/browser/application_context.h
+++ b/ios/chrome/browser/application_context.h
@@ -41,6 +41,10 @@ namespace network_time {
 class NetworkTimeTracker;
 }
 
+namespace physical_web {
+class PhysicalWebDataSource;
+}
+
 namespace rappor {
 class RapporService;
 }
@@ -56,7 +60,6 @@ class VariationsService;
 class ApplicationContext;
 class CRLSetFetcher;
 class IOSChromeIOThread;
-class PhysicalWebDataSource;
 class PrefService;
 
 // Gets the global application context. Cannot return null.
@@ -126,7 +129,7 @@ class ApplicationContext {
   virtual CRLSetFetcher* GetCRLSetFetcher() = 0;
 
   // Gets the PhysicalWebDataSource.
-  virtual PhysicalWebDataSource* GetPhysicalWebDataSource() = 0;
+  virtual physical_web::PhysicalWebDataSource* GetPhysicalWebDataSource() = 0;
 
  protected:
   // Sets the global ApplicationContext instance.