DevTools: allow clearing badge label via passing the empty value in Browser.setDockTile.

TBR: dgozman
Change-Id: I2147e4d4d1c914fed47e9d75859d01a32ea1ce4a
Reviewed-on: https://chromium-review.googlesource.com/c/1341477Reviewed-by: Pavel Feldman <pfeldman@chromium.org>
Commit-Queue: Pavel Feldman <pfeldman@chromium.org>
Cr-Commit-Position: refs/heads/master@{#609135}

chrome/browser/devtools/devtools_dock_tile_mac.mm

@@ -19,7 +19,6 @@ void DevToolsDockTile::Update(const std::string& label, gfx::Image image) {
     [imageView setImage:nsImage];
     [dockTile setContentView:imageView];
   }
-  if (!label.empty())
   [dockTile setBadgeLabel:base::SysUTF8ToNSString(label)];
   [dockTile display];
 }