Mac: don't use a custom tracking area in BridgedContentView

Currently, in BridgedContentView we "opt out"[1] of BaseView's tracking area to install a different one which:
- Specifies `NSTrackingCursorUpdate`
- As a consequence, only tracks while app is active, since the docs say that always tracking is incompatible with cursor updates

However:
- Empirically, cursor updates work fine without this (some test cases: move mouse between Omnibox and other parts of topchrome, move from webcontent links/inputs to topchrome and vice-versa).
- Only tracking while app is active means we don't get entered/exited events from app switching. This means:
  - Switching away from Chrome while showing a topchrome hover tooltip keeps the hover on and makes the tooltip stuck
  - Under some circumstances, hover stops working on switching back to Chrome (see bug)
  - Even though we allow mouse clicks to function when Chrome is inactive (that is, we return `YES` from `acceptsFirstMouse:`, we don't process hovers in this case, contrary to other apps on the system.

This change removes BridgedContentView's tracking area in favor of the default one and gives BaseView some explicit enable/disables, mostly to make tests happy.

[1] By overriding a private method with a no-op!

Bug: 841792

Change-Id: Ifb5d65e22299959b8cac25a9e0a0407650a40746
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2216530Reviewed-by: Elly Fong-Jones <ellyjones@chromium.org>
Reviewed-by: Avi Drissman <avi@chromium.org>
Commit-Queue: Leonard Grey <lgrey@chromium.org>
Cr-Commit-Position: refs/heads/master@{#773848}

components/remote_cocoa/app_shim/bridged_content_view.h

@@ -10,7 +10,6 @@
 #include "base/strings/string16.h"
 #include "components/remote_cocoa/app_shim/remote_cocoa_app_shim_export.h"
 #import "ui/base/cocoa/tool_tip_base_view.h"
-#import "ui/base/cocoa/tracking_area.h"
 
 namespace remote_cocoa {
 class NativeWidgetNSWindowBridge;
@@ -32,9 +31,6 @@ REMOTE_COCOA_APP_SHIM_EXPORT
   // Weak, reset by clearView.
   remote_cocoa::NativeWidgetNSWindowBridge* _bridge;
 
-  // A tracking area installed to enable mouseMoved events.
-  ui::ScopedCrTrackingArea _cursorTrackingArea;
-
   // The keyDown event currently being handled, nil otherwise.
   NSEvent* _keyDownEvent;
 

components/remote_cocoa/app_shim/bridged_content_view.mm

@@ -172,17 +172,6 @@ ui::TextEditCommand GetTextEditCommandForMenuAction(SEL action) {
   if ((self = [super initWithFrame:initialFrame])) {
     _bridge = bridge;
 
-    // Apple's documentation says that NSTrackingActiveAlways is incompatible
-    // with NSTrackingCursorUpdate, so use NSTrackingActiveInActiveApp.
-    _cursorTrackingArea.reset([[CrTrackingArea alloc]
-        initWithRect:NSZeroRect
-             options:NSTrackingMouseMoved | NSTrackingCursorUpdate |
-                     NSTrackingActiveInActiveApp | NSTrackingInVisibleRect |
-                     NSTrackingMouseEnteredAndExited
-               owner:self
-            userInfo:nil]);
-    [self addTrackingArea:_cursorTrackingArea.get()];
-
     // Get notified whenever Full Keyboard Access mode is changed.
     [[NSDistributedNotificationCenter defaultCenter]
         addObserver:self
@@ -227,8 +216,6 @@ ui::TextEditCommand GetTextEditCommandForMenuAction(SEL action) {
 - (void)clearView {
   _bridge = nullptr;
   [[NSDistributedNotificationCenter defaultCenter] removeObserver:self];
-  [_cursorTrackingArea.get() clearOwner];
-  [self removeTrackingArea:_cursorTrackingArea.get()];
 }
 
 - (bool)needsUpdateWindows {
@@ -545,11 +532,6 @@ ui::TextEditCommand GetTextEditCommandForMenuAction(SEL action) {
 
 // BaseView implementation.
 
-// Don't use tracking areas from BaseView. BridgedContentView's tracks
-// NSTrackingCursorUpdate and Apple's documentation suggests it's incompatible.
-- (void)enableTracking {
-}
-
 // Translates the location of |theEvent| to toolkit-views coordinates and passes
 // the event to NativeWidgetMac for handling.
 - (void)mouseEvent:(NSEvent*)theEvent {

ui/base/cocoa/base_view.mm

@@ -12,29 +12,23 @@ NSString* kSelectionDirection = @"Chromium.kSelectionDirection";
 
 @implementation BaseView
 
-- (instancetype)initWithFrame:(NSRect)frame {
-  if ((self = [super initWithFrame:frame])) {
-    [self enableTracking];
-  }
-  return self;
-}
-
-- (instancetype)initWithCoder:(NSCoder*)decoder {
-  if ((self = [super initWithCoder:decoder])) {
-    [self enableTracking];
-  }
-  return self;
-}
 
 - (void)dealloc {
   [self disableTracking];
   [super dealloc];
 }
 
+- (void)viewWillMoveToWindow:(NSWindow*)window {
+  if (window) {
+    [self enableTracking];
+  } else {
+    [self disableTracking];
+  }
+}
+
 - (void)enableTracking {
   if (_trackingArea.get())
     return;
-
   NSTrackingAreaOptions trackingOptions = NSTrackingMouseEnteredAndExited |
                                           NSTrackingMouseMoved |
                                           NSTrackingActiveAlways |