Revert "Never show the close(x) icon on content setting bubbles."

This reverts commit 7cb00345.

Reason for revert: See comment on https://crbug.com/652024#c40. The close (x) should be shown in these instances.

Original change's description:
> Never show the close(x) icon on content setting bubbles.
> 
> Bug: 652024
> Change-Id: I77bfbe29d728e3f3f8bdc0d7d2b1f728d8da969b
> Reviewed-on: https://chromium-review.googlesource.com/740085
> Reviewed-by: Bret Sepulveda <bsep@chromium.org>
> Commit-Queue: Allen Bauer <kylixrd@chromium.org>
> Cr-Commit-Position: refs/heads/master@{#512603}

TBR=bsep@chromium.org,kylixrd@chromium.org

Change-Id: I901d8e394364095ebde746a3aa42e973d8c54868
No-Presubmit: true
No-Tree-Checks: true
No-Try: true
Bug: 652024
Reviewed-on: https://chromium-review.googlesource.com/747041Reviewed-by: Allen Bauer <kylixrd@chromium.org>
Commit-Queue: Allen Bauer <kylixrd@chromium.org>
Cr-Commit-Position: refs/heads/master@{#512838}

chrome/browser/ui/views/content_setting_bubble_contents.cc

@@ -357,7 +357,7 @@ base::string16 ContentSettingBubbleContents::GetWindowTitle() const {
 }
 
 bool ContentSettingBubbleContents::ShouldShowCloseButton() const {
-  return false;
+  return ChromeLayoutProvider::Get()->IsHarmonyMode();
 }
 
 void ContentSettingBubbleContents::Init() {