[PhysicalWeb] Add physical_web namespace.

ios/chrome/common/physical_web/physical_web_scanner.mm

 // Copyright 2015 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #import "ios/chrome/common/physical_web/physical_web_scanner.h"
 
 #import <CoreBluetooth/CoreBluetooth.h>
 
 #include <string>
 #include <vector>
@@ skipping 173 matching lines @@
   for (PhysicalWebDevice* device in [self devices]) {
     std::string scannedUrl =
         base::SysNSStringToUTF8([[device requestURL] absoluteString]);
     std::string resolvedUrl =
         base::SysNSStringToUTF8([[device url] absoluteString]);
     std::string icon = base::SysNSStringToUTF8([[device icon] absoluteString]);
     std::string title = base::SysNSStringToUTF8([device title]);
     std::string description = base::SysNSStringToUTF8([device description]);
 
     auto metadataItem = base::MakeUnique<base::DictionaryValue>();
-    metadataItem->SetString(kPhysicalWebScannedUrlKey, scannedUrl);
-    metadataItem->SetString(kPhysicalWebResolvedUrlKey, resolvedUrl);
-    metadataItem->SetString(kPhysicalWebIconUrlKey, icon);
-    metadataItem->SetString(kPhysicalWebTitleKey, title);
-    metadataItem->SetString(kPhysicalWebDescriptionKey, description);
+    metadataItem->SetString(physical_web::kScannedUrlKey, scannedUrl);
+    metadataItem->SetString(physical_web::kResolvedUrlKey, resolvedUrl);
+    metadataItem->SetString(physical_web::kIconUrlKey, icon);
+    metadataItem->SetString(physical_web::kTitleKey, title);
+    metadataItem->SetString(physical_web::kDescriptionKey, description);
     metadataList->Append(std::move(metadataItem));
   }
 
   return metadataList;
 }
 
 - (void)setNetworkRequestEnabled:(BOOL)enabled {
   if (networkRequestEnabled_ == enabled) {
     return;
   }
@@ skipping 276 matching lines @@
         [strongSelf.get()->devices_ addObject:device];
         [strongSelf.get()->delegate_ scannerUpdatedDevices:weakSelf];
         [strongSelf.get()->finalUrls_ addObject:[device url]];
       }
     }
     [strongSelf.get()->pendingRequests_ removeObject:strongRequest];
   }];
 }
 
 @end