Only show Last N Pages in the UI when the corresponding tab is visible. (cont'd)

Only show Last N Pages in the UI when the corresponding tab is visible.

This patch takes two approaches:
* NTP suggestions now use a DownloadUIAdapter to manage the set of
  items on the page. This adapter is notified about tab addition
  and removal, and only notifies about pages that correspond to a
  tab.
* Deletes pages when a tab is closed.

patch from issue 2684973014 at patchset 180001 (http://crrev.com/2684973014#ps180001)

Note: dewittj@, who is currently OOO, is the original author of this patch
at https://crrev.com/2684973014. I (carlosk@) am taking over it because it
needed addressing of latest comments and I have another change that depends
on this one.

BUG=

Review-Url: https://codereview.chromium.org/2706343007
Cr-Commit-Position: refs/heads/master@{#453685}
Committed: https://chromium.googlesource.com/chromium/src/+/f9671b26418b5a1c11cd23f56e747a3941b78aaa

[carlosk, 2017-02-23 23:16:32]

The CQ bit was checked by carlosk@chromium.org to run a CQ dry run

[commit-bot: I haz the power, 2017-02-23 23:17:32]

Dry run: CQ is trying da patch. Follow status at
 
https://chromium-cq-status.appspot.com/v2/patch-status/codereview.chromium.or...

[carlosk, 2017-02-23 23:18:37]

Patchset #2 (id:20001) has been deleted

[carlosk, 2017-02-23 23:19:38]

The CQ bit was checked by carlosk@chromium.org to run a CQ dry run

[commit-bot: I haz the power, 2017-02-23 23:20:49]

Dry run: CQ is trying da patch. Follow status at
 
https://chromium-cq-status.appspot.com/v2/patch-status/codereview.chromium.or...

[carlosk, 2017-02-23 23:26:05]

carlosk@chromium.org changed reviewers:
+ dimich@google.com, tedchoc@chromium.org, vitaliii@chromium.org

[carlosk, 2017-02-23 23:26:05]

tedchoc@, vitaliii@, dimich@: PTAL.

This is the continuation of the change from dewittj@ you already reviewed at
https://crrev.com/2684973014, plus changes to address tedchoc@'s comments.

[Dmitry Titov, 2017-02-24 01:25:37]

dimich@chromium.org changed reviewers:
+ dimich@chromium.org

[Dmitry Titov, 2017-02-24 01:25:37]

still lgtm from offline pages.

[commit-bot: I haz the power, 2017-02-24 02:20:39]

The CQ bit was unchecked by commit-bot@chromium.org

[commit-bot: I haz the power, 2017-02-24 02:20:40]

Dry run: This issue passed the CQ dry run.

[vitaliii, 2017-02-24 12:36:16]

still lgtm for components/ntp_snippets.

[carlosk, 2017-02-24 18:45:54]

Description was changed from

==========
Only show Last N Pages in the UI when the corresponding tab is visible.

This patch takes two approaches:
* NTP suggestions now use a DownloadUIAdapter to manage the set of
  items on the page. This adapter is notified about tab addition
  and removal, and only notifies about pages that correspond to a
  tab.
* Deletes pages when a tab is closed.

patch from issue 2684973014 at patchset 180001
(http://crrev.com/2684973014#ps180001)

Note: dewittj@, who is currently OOO, is the original author of this patch
at https://crrev.com/2684973014. I (carlosk@) am taking over it because it
needed addressing of latest comments and I have another change that depends
on this one.

BUG=
==========

to

==========
Only show Last N Pages in the UI when the corresponding tab is visible.

This patch takes two approaches:
* NTP suggestions now use a DownloadUIAdapter to manage the set of
  items on the page. This adapter is notified about tab addition
  and removal, and only notifies about pages that correspond to a
  tab.
* Deletes pages when a tab is closed.

patch from issue 2684973014 at patchset 180001
(http://crrev.com/2684973014#ps180001)

Note: dewittj@, who is currently OOO, is the original author of this patch
at https://crrev.com/2684973014. I (carlosk@) am taking over it because it
needed addressing of latest comments and I have another change that depends
on this one.

BUG=
==========

[carlosk, 2017-02-27 21:15:23]

carlosk@chromium.org changed reviewers:
+ dewittj@chromium.org

[Ted C, 2017-02-27 21:33:54]

lgtm (just looked at the ChromeActivity and OfflinePageUtils)

https://codereview.chromium.org/2706343007/diff/50001/chrome/android/java/src...
File
chrome/android/java/src/org/chromium/chrome/browser/offlinepages/OfflinePageUtils.java
(right):

https://codereview.chromium.org/2706343007/diff/50001/chrome/android/java/src...
chrome/android/java/src/org/chromium/chrome/browser/offlinepages/OfflinePageUtils.java:765:
private static Map<ChromeActivity, RecentTabTracker> sTabModelObservers = new
HashMap<>();
nit but I'd put the variable at the top as that is the more common convention

[carlosk, 2017-02-27 21:41:50]

The CQ bit was checked by carlosk@chromium.org

[carlosk, 2017-02-27 21:41:50]

The patchset sent to the CQ was uploaded after l-g-t-m from
vitaliii@chromium.org, dimich@chromium.org, tedchoc@chromium.org
Link to the patchset: https://codereview.chromium.org/2706343007/#ps70001
(title: "Move variable definition up to beginning of file.")

[carlosk, 2017-02-27 21:41:59]

Thanks.

https://codereview.chromium.org/2706343007/diff/50001/chrome/android/java/src...
File
chrome/android/java/src/org/chromium/chrome/browser/offlinepages/OfflinePageUtils.java
(right):

https://codereview.chromium.org/2706343007/diff/50001/chrome/android/java/src...
chrome/android/java/src/org/chromium/chrome/browser/offlinepages/OfflinePageUtils.java:765:
private static Map<ChromeActivity, RecentTabTracker> sTabModelObservers = new
HashMap<>();
On 2017/02/27 21:33:53, Ted C wrote:
> nit but I'd put the variable at the top as that is the more common convention

Done.

[commit-bot: I haz the power, 2017-02-27 21:42:40]

CQ is trying da patch. Follow status at
 
https://chromium-cq-status.appspot.com/v2/patch-status/codereview.chromium.or...

[commit-bot: I haz the power, 2017-02-27 22:47:56]

The CQ bit was unchecked by commit-bot@chromium.org

[commit-bot: I haz the power, 2017-02-27 22:47:57]

Try jobs failed on following builders:
  mac_chromium_rel_ng on master.tryserver.chromium.mac (JOB_FAILED,
http://build.chromium.org/p/tryserver.chromium.mac/builders/mac_chromium_rel_...)

[carlosk, 2017-02-27 22:50:43]

The CQ bit was checked by carlosk@chromium.org

[commit-bot: I haz the power, 2017-02-27 22:51:21]

CQ is trying da patch. Follow status at
 
https://chromium-cq-status.appspot.com/v2/patch-status/codereview.chromium.or...

[commit-bot: I haz the power, 2017-02-27 23:30:43]

The CQ bit was unchecked by commit-bot@chromium.org

[commit-bot: I haz the power, 2017-02-27 23:30:45]

Failed to apply patch for
chrome/android/java/src/org/chromium/chrome/browser/offlinepages/OfflinePageBridge.java:
While running git apply --index -p1;
  error: patch failed:
chrome/android/java/src/org/chromium/chrome/browser/offlinepages/OfflinePageBridge.java:26
  error:
chrome/android/java/src/org/chromium/chrome/browser/offlinepages/OfflinePageBridge.java:
patch does not apply

Patch:      
chrome/android/java/src/org/chromium/chrome/browser/offlinepages/OfflinePageBridge.java
Index:
chrome/android/java/src/org/chromium/chrome/browser/offlinepages/OfflinePageBridge.java
diff --git
a/chrome/android/java/src/org/chromium/chrome/browser/offlinepages/OfflinePageBridge.java
b/chrome/android/java/src/org/chromium/chrome/browser/offlinepages/OfflinePageBridge.java
index
48065c79643bf0f0d7f93f15ebc1549655956099..39057bab40c823fcd374e4affa7f72864fcd2ac9
100644
---
a/chrome/android/java/src/org/chromium/chrome/browser/offlinepages/OfflinePageBridge.java
+++
b/chrome/android/java/src/org/chromium/chrome/browser/offlinepages/OfflinePageBridge.java
@@ -26,6 +26,7 @@ import java.util.Set;
 public class OfflinePageBridge {
     public static final String ASYNC_NAMESPACE = "async_loading";
     public static final String BOOKMARK_NAMESPACE = "bookmark";
+    public static final String LAST_N_NAMESPACE = "last_n";
     public static final String SHARE_NAMESPACE = "share";
 
     /**
@@ -436,6 +437,16 @@ public class OfflinePageBridge {
         nativeCheckPagesExistOffline(mNativeOfflinePageBridge, urlArray,
callbackInternal);
     }
 
+    /** Tells the native side that a new tab has been added for this profile.
*/
+    void registerRecentTab(int tabId) {
+        nativeRegisterRecentTab(mNativeOfflinePageBridge, tabId);
+    }
+
+    /** Tells the native side that a new tab has been removed for this profile.
*/
+    void unregisterRecentTab(int tabId) {
+        nativeUnregisterRecentTab(mNativeOfflinePageBridge, tabId);
+    }
+
     @VisibleForTesting
     static void setOfflineBookmarksEnabledForTesting(boolean enabled) {
         sOfflineBookmarksEnabled = enabled;
@@ -503,12 +514,13 @@ public class OfflinePageBridge {
     private static native boolean nativeIsPageSharingEnabled();
     private static native boolean nativeCanSavePage(String url);
     private static native OfflinePageBridge
nativeGetOfflinePageBridgeForProfile(Profile profile);
-
     @VisibleForTesting
     native void nativeGetAllPages(long nativeOfflinePageBridge,
List<OfflinePageItem> offlinePages,
             final Callback<List<OfflinePageItem>> callback);
     private native void nativeCheckPagesExistOffline(long
nativeOfflinePageBridge, Object[] urls,
             CheckPagesExistOfflineCallbackInternal callback);
+    private native void nativeRegisterRecentTab(long nativeOfflinePageBridge,
int tabId);
+    private native void nativeUnregisterRecentTab(long nativeOfflinePageBridge,
int tabId);
     @VisibleForTesting
     native void nativeGetRequestsInQueue(
             long nativeOfflinePageBridge, Callback<SavePageRequest[]>
callback);

[carlosk, 2017-02-27 23:45:06]

The CQ bit was checked by carlosk@chromium.org

[commit-bot: I haz the power, 2017-02-27 23:45:36]

CQ is trying da patch. Follow status at
 
https://chromium-cq-status.appspot.com/v2/patch-status/codereview.chromium.or...

[commit-bot: I haz the power, 2017-02-27 23:51:18]

The CQ bit was unchecked by commit-bot@chromium.org

[commit-bot: I haz the power, 2017-02-27 23:51:19]

Failed to apply patch for
chrome/android/java/src/org/chromium/chrome/browser/offlinepages/OfflinePageBridge.java:
While running git apply --index -p1;
  error: patch failed:
chrome/android/java/src/org/chromium/chrome/browser/offlinepages/OfflinePageBridge.java:26
  error:
chrome/android/java/src/org/chromium/chrome/browser/offlinepages/OfflinePageBridge.java:
patch does not apply

Patch:      
chrome/android/java/src/org/chromium/chrome/browser/offlinepages/OfflinePageBridge.java
Index:
chrome/android/java/src/org/chromium/chrome/browser/offlinepages/OfflinePageBridge.java
diff --git
a/chrome/android/java/src/org/chromium/chrome/browser/offlinepages/OfflinePageBridge.java
b/chrome/android/java/src/org/chromium/chrome/browser/offlinepages/OfflinePageBridge.java
index
48065c79643bf0f0d7f93f15ebc1549655956099..39057bab40c823fcd374e4affa7f72864fcd2ac9
100644
---
a/chrome/android/java/src/org/chromium/chrome/browser/offlinepages/OfflinePageBridge.java
+++
b/chrome/android/java/src/org/chromium/chrome/browser/offlinepages/OfflinePageBridge.java
@@ -26,6 +26,7 @@ import java.util.Set;
 public class OfflinePageBridge {
     public static final String ASYNC_NAMESPACE = "async_loading";
     public static final String BOOKMARK_NAMESPACE = "bookmark";
+    public static final String LAST_N_NAMESPACE = "last_n";
     public static final String SHARE_NAMESPACE = "share";
 
     /**
@@ -436,6 +437,16 @@ public class OfflinePageBridge {
         nativeCheckPagesExistOffline(mNativeOfflinePageBridge, urlArray,
callbackInternal);
     }
 
+    /** Tells the native side that a new tab has been added for this profile.
*/
+    void registerRecentTab(int tabId) {
+        nativeRegisterRecentTab(mNativeOfflinePageBridge, tabId);
+    }
+
+    /** Tells the native side that a new tab has been removed for this profile.
*/
+    void unregisterRecentTab(int tabId) {
+        nativeUnregisterRecentTab(mNativeOfflinePageBridge, tabId);
+    }
+
     @VisibleForTesting
     static void setOfflineBookmarksEnabledForTesting(boolean enabled) {
         sOfflineBookmarksEnabled = enabled;
@@ -503,12 +514,13 @@ public class OfflinePageBridge {
     private static native boolean nativeIsPageSharingEnabled();
     private static native boolean nativeCanSavePage(String url);
     private static native OfflinePageBridge
nativeGetOfflinePageBridgeForProfile(Profile profile);
-
     @VisibleForTesting
     native void nativeGetAllPages(long nativeOfflinePageBridge,
List<OfflinePageItem> offlinePages,
             final Callback<List<OfflinePageItem>> callback);
     private native void nativeCheckPagesExistOffline(long
nativeOfflinePageBridge, Object[] urls,
             CheckPagesExistOfflineCallbackInternal callback);
+    private native void nativeRegisterRecentTab(long nativeOfflinePageBridge,
int tabId);
+    private native void nativeUnregisterRecentTab(long nativeOfflinePageBridge,
int tabId);
     @VisibleForTesting
     native void nativeGetRequestsInQueue(
             long nativeOfflinePageBridge, Callback<SavePageRequest[]>
callback);

[carlosk, 2017-02-27 23:56:46]

The CQ bit was checked by carlosk@chromium.org

[carlosk, 2017-02-27 23:56:47]

The patchset sent to the CQ was uploaded after l-g-t-m from
tedchoc@chromium.org, vitaliii@chromium.org, dimich@chromium.org
Link to the patchset: https://codereview.chromium.org/2706343007/#ps90001
(title: "Rebase.")

[commit-bot: I haz the power, 2017-02-27 23:57:34]

CQ is trying da patch. Follow status at
 
https://chromium-cq-status.appspot.com/v2/patch-status/codereview.chromium.or...

[commit-bot: I haz the power, 2017-02-28 01:19:42]

The CQ bit was unchecked by commit-bot@chromium.org

[commit-bot: I haz the power, 2017-02-28 01:19:43]

Failed to apply patch for
components/offline_pages/core/downloads/download_ui_adapter.cc:
While running git apply --index -p1;
  error: patch failed:
components/offline_pages/core/downloads/download_ui_adapter.cc:18
  error: components/offline_pages/core/downloads/download_ui_adapter.cc: patch
does not apply

Patch:       components/offline_pages/core/downloads/download_ui_adapter.cc
Index: components/offline_pages/core/downloads/download_ui_adapter.cc
diff --git a/components/offline_pages/core/downloads/download_ui_adapter.cc
b/components/offline_pages/core/downloads/download_ui_adapter.cc
index
d73ed686aa5e8b2a72f52bde5354e0da75e98e80..607652964a27c5cfe2b103cf3ad84930d401e771
100644
--- a/components/offline_pages/core/downloads/download_ui_adapter.cc
+++ b/components/offline_pages/core/downloads/download_ui_adapter.cc
@@ -1,4 +1,4 @@
-// Copyright 2016 The Chromium Authors. All rights reserved.
+// Copyright 2017 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.
 
@@ -18,19 +18,21 @@
 
 namespace offline_pages {
 
-DownloadUIAdapter::ItemInfo::ItemInfo(const OfflinePageItem& page)
+DownloadUIAdapter::ItemInfo::ItemInfo(const OfflinePageItem& page,
+                                      bool temporarily_hidden)
     : ui_item(base::MakeUnique<DownloadUIItem>(page)),
       is_request(false),
       offline_id(page.offline_id),
       client_id(page.client_id),
-      temporarily_hidden(false) {}
+      temporarily_hidden(temporarily_hidden) {}
 
-DownloadUIAdapter::ItemInfo::ItemInfo(const SavePageRequest& request)
+DownloadUIAdapter::ItemInfo::ItemInfo(const SavePageRequest& request,
+                                      bool temporarily_hidden)
     : ui_item(base::MakeUnique<DownloadUIItem>(request)),
       is_request(true),
       offline_id(request.request_id()),
       client_id(request.client_id()),
-      temporarily_hidden(false) {}
+      temporarily_hidden() {}
 
 DownloadUIAdapter::ItemInfo::~ItemInfo() {}
 
@@ -42,7 +44,9 @@ DownloadUIAdapter::DownloadUIAdapter(OfflinePageModel* model,
       delegate_(std::move(delegate)),
       state_(State::NOT_LOADED),
       observers_count_(0),
-      weak_ptr_factory_(this) {}
+      weak_ptr_factory_(this) {
+  delegate_->SetUIAdapter(this);
+}
 
 DownloadUIAdapter::~DownloadUIAdapter() {}
 
@@ -85,7 +89,9 @@ void DownloadUIAdapter::OfflinePageAdded(OfflinePageModel*
model,
   if (!delegate_->IsVisibleInUI(added_page.client_id))
     return;
 
-  AddItemHelper(base::MakeUnique<ItemInfo>(added_page));
+  bool temporarily_hidden =
+      delegate_->IsTemporarilyHiddenInUI(added_page.client_id);
+  AddItemHelper(base::MakeUnique<ItemInfo>(added_page, temporarily_hidden));
 }
 
 void DownloadUIAdapter::OfflinePageDeleted(int64_t offline_id,
@@ -100,7 +106,9 @@ void DownloadUIAdapter::OnAdded(const SavePageRequest&
added_request) {
   if (!delegate_->IsVisibleInUI(added_request.client_id()))
     return;
 
-  AddItemHelper(base::MakeUnique<ItemInfo>(added_request));
+  bool temporarily_hidden =
+      delegate_->IsTemporarilyHiddenInUI(added_request.client_id());
+  AddItemHelper(base::MakeUnique<ItemInfo>(added_request, temporarily_hidden));
 }
 
 // RequestCoordinator::Observer
@@ -123,7 +131,9 @@ void DownloadUIAdapter::OnChanged(const SavePageRequest&
request) {
     return;
 
   std::string guid = request.client_id().id;
-  items_[guid] = base::MakeUnique<ItemInfo>(request);
+  bool temporarily_hidden =
+      delegate_->IsTemporarilyHiddenInUI(request.client_id());
+  items_[guid] = base::MakeUnique<ItemInfo>(request, temporarily_hidden);
 
   if (state_ != State::LOADED)
     return;
@@ -186,6 +196,9 @@ void DownloadUIAdapter::DeleteItem(const std::string& guid)
{
 }
 
 int64_t DownloadUIAdapter::GetOfflineIdByGuid(const std::string& guid) const {
+  if (deleting_item_ && deleting_item_->ui_item->guid == guid)
+    return deleting_item_->offline_id;
+
   DownloadUIItems::const_iterator it = items_.find(guid);
   if (it != items_.end())
     return it->second->offline_id;
@@ -235,9 +248,10 @@ void DownloadUIAdapter::OnOfflinePagesLoaded(
     if (delegate_->IsVisibleInUI(page.client_id)) {
       std::string guid = page.client_id.id;
       DCHECK(items_.find(guid) == items_.end());
-      std::unique_ptr<ItemInfo> item = base::MakeUnique<ItemInfo>(page);
-      item->temporarily_hidden =
+      bool temporarily_hidden =
           delegate_->IsTemporarilyHiddenInUI(page.client_id);
+      std::unique_ptr<ItemInfo> item =
+          base::MakeUnique<ItemInfo>(page, temporarily_hidden);
       items_[guid] = std::move(item);
     }
   }
@@ -260,10 +274,10 @@ void DownloadUIAdapter::OnRequestsLoaded(
     if (delegate_->IsVisibleInUI(request->client_id())) {
       std::string guid = request->client_id().id;
       DCHECK(items_.find(guid) == items_.end());
-      std::unique_ptr<ItemInfo> item =
-          base::MakeUnique<ItemInfo>(*request.get());
-      item->temporarily_hidden =
+      bool temporarily_hidden =
           delegate_->IsTemporarilyHiddenInUI(request->client_id());
+      std::unique_ptr<ItemInfo> item =
+          base::MakeUnique<ItemInfo>(*request.get(), temporarily_hidden);
       items_[guid] = std::move(item);
     }
   }
@@ -300,27 +314,35 @@ void
DownloadUIAdapter::AddItemHelper(std::unique_ptr<ItemInfo> item_info) {
     return;
 
   DownloadUIItem* download_ui_item = items_[guid]->ui_item.get();
+
   if (request_to_page_transition) {
     download_ui_item->download_state = DownloadUIItem::DownloadState::COMPLETE;
-    for (Observer& observer : observers_)
-      observer.ItemUpdated(*download_ui_item);
+    if (!items_[guid]->temporarily_hidden) {
+      for (Observer& observer : observers_)
+        observer.ItemUpdated(*download_ui_item);
+    }
   } else {
-    for (Observer& observer : observers_)
-      observer.ItemAdded(*download_ui_item);
+    if (!items_[guid]->temporarily_hidden) {
+      for (Observer& observer : observers_)
+        observer.ItemAdded(*download_ui_item);
+    }
   }
 }
 
 void DownloadUIAdapter::DeleteItemHelper(const std::string& guid) {
-  DownloadUIItems::const_iterator it = items_.find(guid);
+  DownloadUIItems::iterator it = items_.find(guid);
   if (it == items_.end())
     return;
+  DCHECK(deleting_item_ == nullptr);
+  deleting_item_ = std::move(it->second);
   items_.erase(it);
 
-  if (state_ != State::LOADED)
-    return;
+  if (!deleting_item_->temporarily_hidden && state_ == State::LOADED) {
+    for (Observer& observer : observers_)
+      observer.ItemDeleted(guid);
+  }
 
-  for (Observer& observer : observers_)
-    observer.ItemDeleted(guid);
+  deleting_item_.reset();
 }
 
 }  // namespace offline_pages

[carlosk, 2017-02-28 18:37:19]

The CQ bit was checked by carlosk@chromium.org

[carlosk, 2017-02-28 18:37:19]

The patchset sent to the CQ was uploaded after l-g-t-m from
tedchoc@chromium.org, vitaliii@chromium.org, dimich@chromium.org
Link to the patchset: https://codereview.chromium.org/2706343007/#ps110001
(title: "Rebase.")

[commit-bot: I haz the power, 2017-02-28 18:37:49]

CQ is trying da patch. Follow status at
 
https://chromium-cq-status.appspot.com/v2/patch-status/codereview.chromium.or...

[dewittj, 2017-02-28 18:38:22]

I think if this doesn't go through you should just git-cl land it.

[commit-bot: I haz the power, 2017-02-28 20:21:46]

CQ is committing da patch.

Bot data: {"patchset_id": 110001, "attempt_start_ts": 1488307039125480,
"parent_rev": "aa40908dd04900048559b86f7eeae484e6623e11", "commit_rev":
"f9671b26418b5a1c11cd23f56e747a3941b78aaa"}

[commit-bot: I haz the power, 2017-02-28 20:22:28]

Description was changed from

==========
Only show Last N Pages in the UI when the corresponding tab is visible.

This patch takes two approaches:
* NTP suggestions now use a DownloadUIAdapter to manage the set of
  items on the page. This adapter is notified about tab addition
  and removal, and only notifies about pages that correspond to a
  tab.
* Deletes pages when a tab is closed.

patch from issue 2684973014 at patchset 180001
(http://crrev.com/2684973014#ps180001)

Note: dewittj@, who is currently OOO, is the original author of this patch
at https://crrev.com/2684973014. I (carlosk@) am taking over it because it
needed addressing of latest comments and I have another change that depends
on this one.

BUG=
==========

to

==========
Only show Last N Pages in the UI when the corresponding tab is visible.

This patch takes two approaches:
* NTP suggestions now use a DownloadUIAdapter to manage the set of
  items on the page. This adapter is notified about tab addition
  and removal, and only notifies about pages that correspond to a
  tab.
* Deletes pages when a tab is closed.

patch from issue 2684973014 at patchset 180001
(http://crrev.com/2684973014#ps180001)

Note: dewittj@, who is currently OOO, is the original author of this patch
at https://crrev.com/2684973014. I (carlosk@) am taking over it because it
needed addressing of latest comments and I have another change that depends
on this one.

BUG=

Review-Url: https://codereview.chromium.org/2706343007
Cr-Commit-Position: refs/heads/master@{#453685}
Committed:
https://chromium.googlesource.com/chromium/src/+/f9671b26418b5a1c11cd23f56e74...
==========

[commit-bot: I haz the power, 2017-02-28 20:22:30]

Committed patchset #6 (id:110001) as
https://chromium.googlesource.com/chromium/src/+/f9671b26418b5a1c11cd23f56e74...