Add a Physical Web data source

ios/chrome/common/physical_web/ios_chrome_physical_web_data_source.mm

+// Copyright 2016 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/ios_chrome_physical_web_data_source.h"
+
+#include "base/memory/ptr_util.h"
+
+IOSChromePhysicalWebDataSource::IOSChromePhysicalWebDataSource() {}
+
+IOSChromePhysicalWebDataSource::~IOSChromePhysicalWebDataSource() {
+  StopDiscovery();
+}
+
+void IOSChromePhysicalWebDataSource::StartDiscovery(
+    bool network_request_enabled) {
+  // If there are unresolved beacons it means the scanner is started but does
+  // not have network requests enabled. In this case we should avoid recreating
+  // the scanner as it would clear the cache of nearby beacons.
+  if (network_request_enabled && HasUnresolvedDiscoveries()) {
+    [scanner_ setNetworkRequestEnabled:YES];
+    return;
+  }
+
+  [scanner_ stop];
+  scanner_.reset([[PhysicalWebScanner alloc] initWithDelegate:nil]);
+  [scanner_ setNetworkRequestEnabled:network_request_enabled];
+  [scanner_ start];
+}
+
+void IOSChromePhysicalWebDataSource::StopDiscovery() {
+  [scanner_ stop];
+  scanner_.reset();
+}
+
+std::unique_ptr<base::ListValue> IOSChromePhysicalWebDataSource::GetMetadata() {
+  std::unique_ptr<base::ListValue> metadata = [scanner_ metadata];

[sdefresne, 2016/08/04 19:23:47]

It look like the current implementation of -[PhysicalWebScanner metadata] always
returns a non-nil object, so the check below is redundant. Can we instead change
it to DCHECK(metadata)? This would require including base/logging.h.

[mattreynolds, 2016/08/04 21:14:34]

Done.

+  if (!metadata) {
+    metadata = base::MakeUnique<base::ListValue>();
+  }
+  return metadata;
+}
+
+bool IOSChromePhysicalWebDataSource::HasUnresolvedDiscoveries() {
+  return [scanner_ unresolvedBeaconsCount] > 0;
+}