[ios clean] Add placeholder for NTP bookmarks, chrome home and open tabs.

ios/clean/chrome/browser/ui/tab/tab_coordinator.mm

Index: ios/clean/chrome/browser/ui/tab/tab_coordinator.mm
diff --git a/ios/clean/chrome/browser/ui/tab/tab_coordinator.mm b/ios/clean/chrome/browser/ui/tab/tab_coordinator.mm
index 59497cb2e159e0165b1fa94e3b025c0ca8759c21..e96fac04c9e050c5bba7e7e33f9d0b34f4731e3d 100644
--- a/ios/clean/chrome/browser/ui/tab/tab_coordinator.mm
+++ b/ios/clean/chrome/browser/ui/tab/tab_coordinator.mm
@@ -32,6 +32,8 @@ const BOOL kUseBottomToolbar = NO;
 @interface TabCoordinator ()<CRWWebStateObserver,
                              UIViewControllerTransitioningDelegate>
 @property(nonatomic, strong) TabContainerViewController* viewController;
+@property(nonatomic, weak) NTPCoordinator* ntpCoordinator;
+@property(nonatomic, weak) WebCoordinator* webCoordinator;
 @end
 
 @implementation TabCoordinator {
@@ -41,6 +43,8 @@ const BOOL kUseBottomToolbar = NO;
 @synthesize presentationKey = _presentationKey;
 @synthesize viewController = _viewController;
 @synthesize webState = _webState;
+@synthesize webCoordinator = _webCoordinator;
+@synthesize ntpCoordinator = _ntpCoordinator;
 
 #pragma mark - BrowserCoordinator
 
@@ -58,6 +62,7 @@ const BOOL kUseBottomToolbar = NO;
   // view controller.
   webCoordinator.context.baseViewController = nil;
   [webCoordinator start];
+  self.webCoordinator = webCoordinator;
 
   ToolbarCoordinator* toolbarCoordinator = [[ToolbarCoordinator alloc] init];
   toolbarCoordinator.webState = self.webState;
@@ -73,9 +78,19 @@ const BOOL kUseBottomToolbar = NO;
   tabStripCoordinator.context.baseViewController = nil;
   [tabStripCoordinator start];
 
+  // PLACEHOLDER: Fix the order of events here. The ntpCoordinator was already
+  // created above when |webCoordinator.webState = self.webState;| triggers
+  // a load event, but then the webCoordinator stomps on the
+  // contentViewController when it starts afterwards.
+  if (self.webState->GetLastCommittedURL() == GURL("chrome://newtab/")) {
+    self.viewController.contentViewController =
+        self.ntpCoordinator.viewController;
+  }
+
   [self.context.baseViewController presentViewController:self.viewController
                                                 animated:self.context.animated
                                               completion:nil];
+
   [super start];
 }
 
@@ -86,6 +101,9 @@ const BOOL kUseBottomToolbar = NO;
   for (BrowserCoordinator* child in self.children) {
     [child stop];
   }
+
+  [self.viewController setContentViewController:nil];
+
   [self.viewController.presentingViewController
       dismissViewControllerAnimated:self.context.animated
                          completion:nil];
@@ -99,6 +117,8 @@ const BOOL kUseBottomToolbar = NO;
     self.viewController.contentViewController = coordinator.viewController;
   } else if ([coordinator isKindOfClass:[TabStripCoordinator class]]) {
     self.viewController.tabStripViewController = coordinator.viewController;
+  } else if ([coordinator isKindOfClass:[NTPCoordinator class]]) {
+    self.viewController.contentViewController = coordinator.viewController;
   }
 }
 
@@ -129,8 +149,19 @@ const BOOL kUseBottomToolbar = NO;
     NTPCoordinator* ntpCoordinator = [[NTPCoordinator alloc] init];
     [self addChildCoordinator:ntpCoordinator];
     ntpCoordinator.context.baseViewController = nil;
+    ntpCoordinator.webState = self.webState;
     [ntpCoordinator start];
-    self.viewController.contentViewController = ntpCoordinator.viewController;
+    self.ntpCoordinator = ntpCoordinator;
+  }
+}
+
+- (void)webState:(web::WebState*)webState
+    didStartProvisionalNavigationForURL:(const GURL&)URL {
+  if (self.ntpCoordinator) {
+    [self.ntpCoordinator stop];
+    [self removeChildCoordinator:self.ntpCoordinator];
+    self.viewController.contentViewController =
+        self.webCoordinator.viewController;
   }
 }