[Extensions Toolbar Mac] Adjust equality comparisons in container code

Adjust from using strict equality to >= and <= in order to account for the
possibility of ratios and floats more safely.

BUG=463905

Review URL: https://codereview.chromium.org/1025303003

Cr-Commit-Position: refs/heads/master@{#321834}

chrome/browser/ui/cocoa/extensions/browser_actions_container_view.mm

@@ -168,10 +168,10 @@ const CGFloat kMinimumContainerWidth = 3.0;
   if ((dX < 0.0 && !canDragLeft_) || (dX > 0.0 && !canDragRight_))
     return;
 
-  if (NSWidth(containerFrame) == kMinimumContainerWidth)
+  if (NSWidth(containerFrame) <= kMinimumContainerWidth)
     return;
 
-  grippyPinned_ = NSWidth(containerFrame) == maxAllowedWidth;
+  grippyPinned_ = NSWidth(containerFrame) >= maxAllowedWidth;
   containerFrame.origin.x += dX;
 
   [self setFrame:containerFrame];