[Mac] Moved TextSuggestionsTouchBarController's Range Validity Check

Previously, -updateTextSelection:range:offset: could receive an invalid
range from WebContentsTextObserver::DidChangeTextSelection(). This
invalid range would then cause a crash in -requestSuggestions.

A check has been added to -updateTextSelection:range:offset: to make
sure that a selection with an invalid range is not passed to
-requestSuggestions. This should prevent future crashes.

TextSuggestionsTouchBarControllerTest.InvalidRange tests that an
invalid range does not crash the controller and is handled
properly.

Bug: 717553
Change-Id: I69f49cb1f1819e1d528837767dfb894d8652e84d
Reviewed-on: https://chromium-review.googlesource.com/1178467Reviewed-by: Avi Drissman <avi@chromium.org>
Reviewed-by: Sarah Chan <spqchan@chromium.org>
Commit-Queue: Tessa Nijssen <tnijssen@google.com>
Cr-Commit-Position: refs/heads/master@{#583815}

chrome/browser/ui/cocoa/touchbar/text_suggestions_touch_bar_controller.mm

@@ -173,6 +173,11 @@ class WebContentsTextObserver : public content::WebContentsObserver {
       return;
     }
 
+    if (!range.IsValid()) {
+      [self updateTextSelection:base::string16() range:gfx::Range() offset:0];
+      return;
+    }
+
     text_.reset([base::SysUTF16ToNSString(text) retain]);
     selectionRange_ =
         NSMakeRange(range.start() - offset, range.end() - range.start());
@@ -271,10 +276,8 @@ class WebContentsTextObserver : public content::WebContentsObserver {
       webContents_->GetTopLevelRenderWidgetHostView()->GetSelectedRange();
   const size_t offset = webContents_->GetTopLevelRenderWidgetHostView()
                             ->GetOffsetForSurroundingText();
-  if (range.IsValid())
+
   [self updateTextSelection:text range:range offset:offset];
-  else
-    [self updateTextSelection:base::string16() range:gfx::Range() offset:0];
 }
 
 - (content::WebContents*)webContents {

chrome/browser/ui/cocoa/touchbar/text_suggestions_touch_bar_controller_browsertest.mm

@@ -191,6 +191,17 @@ IN_PROC_BROWSER_TEST_F(TextSuggestionsTouchBarControllerTest,
   }
 }
 
+// Tests that an invalid range does not crash the controller.
+IN_PROC_BROWSER_TEST_F(TextSuggestionsTouchBarControllerTest, InvalidRange) {
+  FocusTextfield();
+  [touch_bar_controller_
+      updateTextSelection:base::string16(base::ASCIIToUTF16("text"))
+                    range:gfx::Range::InvalidRange()
+                   offset:0];
+  EXPECT_STREQ("", [touch_bar_controller_ text].UTF8String);
+  EXPECT_EQ(gfx::Range(), [touch_bar_controller_ selectionRange]);
+}
+
 // Tests that a change in WebContents is handled properly.
 IN_PROC_BROWSER_TEST_F(TextSuggestionsTouchBarControllerTest, SetWebContents) {
   NSString* const kText = @"text";