[Mac] Move selection validation to a Touch Bar-specific place.

Effectively changes three things from r612882:
1. Reverts the checks in OnTextSelectionChanged(). This drops
   DumpWithoutCrashing(), which was louder than intended, and avoids
   potentially changing non-Touch Bar behavior.
2. Preserves the new behavior of ignoring an invalid selection instead of
   clearing the existing suggestions by removing the selection-clearing code.
3. Adds a bounds check that was removed in (1) into Touch Bar code.

Bug: 893038, 910950
Change-Id: I6fdb30a71ce64680fb06ce73072c9171da36da32
Reviewed-on: https://chromium-review.googlesource.com/c/1358695Reviewed-by: Elly Fong-Jones <ellyjones@chromium.org>
Commit-Queue: Sidney San Martín <sdy@chromium.org>
Cr-Commit-Position: refs/heads/master@{#613105}

content/browser/renderer_host/render_widget_host_view_cocoa.mm

@@ -250,19 +250,15 @@ void ExtractUnderlines(NSAttributedString* string,
       updateWithInsertionPointVisibility:textSelectionRange_.is_empty()];
   if (!touchBarItem.candidateListVisible)
     return;
-  if (!textSelectionRange_.IsValid()) {
-    [touchBarItem setCandidates:@[]
-               forSelectedRange:NSMakeRange(NSNotFound, 0)
-                       inString:nil];
-
-    // Bump the sequence number so that any request in flight is ignored.
-    textSuggestionsSequenceNumber_ += 1;
+  if (!textSelectionRange_.IsValid() ||
+      textSelectionOffset_ > textSelectionRange_.GetMin())
     return;
-  }
 
   NSRange selectionRange = textSelectionRange_.ToNSRange();
   NSString* selectionText = base::SysUTF16ToNSString(textSelectionText_);
   selectionRange.location -= textSelectionOffset_;
+  if (NSMaxRange(selectionRange) > selectionText.length)
+    return;
   NSSpellChecker* spell_checker = spellCheckerForTesting_
                                       ? spellCheckerForTesting_
                                       : [NSSpellChecker sharedSpellChecker];

content/browser/renderer_host/render_widget_host_view_mac.mm

@@ -11,7 +11,6 @@
 
 #include "base/bind.h"
 #include "base/command_line.h"
-#include "base/debug/dump_without_crashing.h"
 #include "base/feature_list.h"
 #include "base/logging.h"
 #include "base/mac/mac_util.h"
@@ -657,23 +656,6 @@ void RenderWidgetHostViewMac::OnTextSelectionChanged(
   if (!selection)
     return;
 
-  if (!selection->range().IsValid()) {
-    LOG(ERROR) << "Invalid selection range.";
-    base::debug::DumpWithoutCrashing();
-    return;
-  }
-
-  gfx::Range text_range(selection->offset(),
-                        selection->text().length() + selection->offset());
-  if (selection->range().GetMin() < text_range.GetMin() ||
-      selection->range().GetMax() > text_range.GetMax()) {
-    LOG(ERROR) << "Selection with range " << selection->range().ToString()
-               << " in a chunk of text which only covers "
-               << text_range.ToString() << ".";
-    base::debug::DumpWithoutCrashing();
-    return;
-  }
-
   ns_view_bridge_->SetTextSelection(selection->text(), selection->offset(),
                                     selection->range());
 }