RemoteRWHVMac: Fix missed nullptr check in firstRectForCharacterRange

In crrev.com/549621, the RenderWidgetHostViewCocoa method
firstRectForCharacterRange was changed from doing an early-out if
!renderWidgetHostView_->GetFocusedWidget() to doing an early-out if
clientWasDestroyed_.

These are not the same thing -- clientWasDestroyed_ is equivalent to
checking host(). Now we're seeing crashes downstream because
OnNSViewSyncGetFirstRectForRange is getting called when
renderWidgetHostView_->GetFocusedWidget() is nullptr.

Fold firstViewRectForCharacterRange into firstRectForCharacterRange,
(since it had no other callers), and update the synchronous method
OnNSViewSyncGetFirstRectForRange to query GetFocusedWidget() and
return a success parameter indicating if it is non-nullptr.

Bug: 835272, 821651
Change-Id: I5063ed3c154cc1c1efc1f1e903153efc9aef66d1
Reviewed-on: https://chromium-review.googlesource.com/1024411
Commit-Queue: ccameron <ccameron@chromium.org>
Reviewed-by: ccameron <ccameron@chromium.org>
Reviewed-by: Sidney San Martín <sdy@chromium.org>
Cr-Commit-Position: refs/heads/master@{#552856}

content/browser/renderer_host/render_widget_host_ns_view_client.h

@@ -128,11 +128,13 @@ class RenderWidgetHostNSViewClient {
 
   // Synchronously query the composition character boundary rectangle and return
   // it in |*rect|. Set |*actual_range| to the range actually used for the
-  // returned rectangle.
+  // returned rectangle. If there was no focused RenderWidgetHost to query,
+  // then set |*success| to false.
   virtual void OnNSViewSyncGetFirstRectForRange(
       const gfx::Range& requested_range,
       gfx::Rect* rect,
-      gfx::Range* actual_range) = 0;
+      gfx::Range* actual_range,
+      bool* success) = 0;
 
   // Forward the corresponding edit menu command to the RenderWidgetHost's
   // delegate.

content/browser/renderer_host/render_widget_host_view_cocoa.h

@@ -199,8 +199,6 @@ struct DidOverscrollParams;
 // Confirm ongoing composition.
 - (void)finishComposingText;
 - (void)updateCursor:(NSCursor*)cursor;
-- (NSRect)firstViewRectForCharacterRange:(NSRange)theRange
-                             actualRange:(NSRangePointer)actualRange;
 - (void)tabletEvent:(NSEvent*)theEvent;
 - (void)quickLookWithEvent:(NSEvent*)event;
 - (void)showLookUpDictionaryOverlayFromRange:(NSRange)range;

content/browser/renderer_host/render_widget_host_view_cocoa.mm

@@ -107,7 +107,8 @@ class NoopClient : public RenderWidgetHostNSViewClient {
                                             uint32_t* index) override {}
   void OnNSViewSyncGetFirstRectForRange(const gfx::Range& requested_range,
                                         gfx::Rect* rect,
-                                        gfx::Range* actual_range) override {}
+                                        gfx::Range* actual_range,
+                                        bool* success) override {}
   void OnNSViewExecuteEditCommand(const std::string& command) override {}
   void OnNSViewUndo() override {}
   void OnNSViewRedo() override {}
@@ -1487,34 +1488,28 @@ extern NSString* NSTextInputReplacementRangeAttributeName;
   return NSUInteger(char_index);
 }
 
-- (NSRect)firstViewRectForCharacterRange:(NSRange)theRange
-                             actualRange:(NSRangePointer)actualRange {
+- (NSRect)firstRectForCharacterRange:(NSRange)theRange
+                         actualRange:(NSRangePointer)actualRange {
   gfx::Rect gfxRect;
   gfx::Range gfxActualRange;
+  bool success = false;
   if (actualRange)
     gfxActualRange = gfx::Range(*actualRange);
   client_->OnNSViewSyncGetFirstRectForRange(gfx::Range(theRange), &gfxRect,
-                                            &gfxActualRange);
+                                            &gfxActualRange, &success);
+  if (!success) {
+    // The call to cancelComposition comes from https://crrev.com/350261.
+    [self cancelComposition];
+    return NSZeroRect;
+  }
   if (actualRange)
     *actualRange = gfxActualRange.ToNSRange();
 
   // The returned rectangle is in WebKit coordinates (upper left origin), so
   // flip the coordinate system.
   NSRect viewFrame = [self frame];
-  NSRect flippedRect = NSRectFromCGRect(gfxRect.ToCGRect());
-  flippedRect.origin.y = NSHeight(viewFrame) - NSMaxY(flippedRect);
-  return flippedRect;
-}
-
-- (NSRect)firstRectForCharacterRange:(NSRange)theRange
-                         actualRange:(NSRangePointer)actualRange {
-  if ([self clientIsDisconnected]) {
-    [self cancelComposition];
-    return NSZeroRect;
-  }
-
-  NSRect rect =
-      [self firstViewRectForCharacterRange:theRange actualRange:actualRange];
+  NSRect rect = NSRectFromCGRect(gfxRect.ToCGRect());
+  rect.origin.y = NSHeight(viewFrame) - NSMaxY(rect);
 
   // Convert into screen coordinates for return.
   rect = [self convertRect:rect toView:nil];

content/browser/renderer_host/render_widget_host_view_mac.h

@@ -334,7 +334,8 @@ class CONTENT_EXPORT RenderWidgetHostViewMac
                                             uint32_t* index) override;
   void OnNSViewSyncGetFirstRectForRange(const gfx::Range& requested_range,
                                         gfx::Rect* rect,
-                                        gfx::Range* actual_range) override;
+                                        gfx::Range* actual_range,
+                                        bool* success) override;
   void OnNSViewExecuteEditCommand(const std::string& command) override;
   void OnNSViewUndo() override;
   void OnNSViewRedo() override;

content/browser/renderer_host/render_widget_host_view_mac.mm

@@ -1540,7 +1540,13 @@ void RenderWidgetHostViewMac::OnNSViewSyncGetCharacterIndexAtPoint(
 void RenderWidgetHostViewMac::OnNSViewSyncGetFirstRectForRange(
     const gfx::Range& requested_range,
     gfx::Rect* rect,
-    gfx::Range* actual_range) {
+    gfx::Range* actual_range,
+    bool* success) {
+  if (!GetFocusedWidget()) {
+    *success = false;
+    return;
+  }
+  *success = true;
   if (!GetCachedFirstRectForCharacterRange(requested_range, rect,
                                            actual_range)) {
     *rect = TextInputClientMac::GetInstance()->GetFirstRectForRange(