Revert "Disable OverflowButtonInkDropTest.MouseContextMenu on linux"

This reverts commit dd0ab32b.

Reason for revert: <INSERT REASONING HERE>
CL causes the crash has been reverted

Original change's description:
> Disable OverflowButtonInkDropTest.MouseContextMenu on linux
> 
> TBR=wjmaclean@chromium.org
> NOTRY=true
> 
> Bug: 874853
> Change-Id: I0e28c54f5dfbfa0ae940b48ea5319914e6b49768
> Reviewed-on: https://chromium-review.googlesource.com/1177684
> Reviewed-by: Xida Chen <xidachen@chromium.org>
> Commit-Queue: Xida Chen <xidachen@chromium.org>
> Cr-Commit-Position: refs/heads/master@{#583634}

TBR=xidachen@chromium.org

Change-Id: I8d74e83b26a7f89eb7dc11323a8198c848a36fb5
No-Presubmit: true
No-Tree-Checks: true
No-Try: true
Bug: 874853
Reviewed-on: https://chromium-review.googlesource.com/1178262Reviewed-by: Xida Chen <xidachen@chromium.org>
Commit-Queue: Xida Chen <xidachen@chromium.org>
Cr-Commit-Position: refs/heads/master@{#583710}

ash/shelf/shelf_view_unittest.cc

@@ -2935,14 +2935,9 @@ TEST_F(OverflowButtonInkDropTest, MouseDragOutAndBack) {
   ASSERT_TRUE(test_api_->IsShowingOverflowBubble());
 }
 
-#if defined(OS_LINUX)
-#define MAYBE_MouseContextMenu DISABLED_MouseContextMenu
-#else
-#define MAYBE_MouseContextMenu MouseContextMenu
-#endif
 // Tests ink drop state transitions for the overflow button when the user
 // right clicks on the button to show the context menu.
-TEST_F(OverflowButtonInkDropTest, MAYBE_MouseContextMenu) {
+TEST_F(OverflowButtonInkDropTest, MouseContextMenu) {
   ui::test::EventGenerator* generator = GetEventGenerator();
   generator->MoveMouseTo(GetScreenPointInsideOverflowButton());