Enable user resizing for docked Panels (GTK and Mac).

chrome/browser/ui/panels/panel_overflow_browsertest.cc

Index: chrome/browser/ui/panels/panel_overflow_browsertest.cc
diff --git a/chrome/browser/ui/panels/panel_overflow_browsertest.cc b/chrome/browser/ui/panels/panel_overflow_browsertest.cc
index 12a4a2fbf4d0dad15c2cd2b255584e80f4558fcd..315592ca40b07d519a5262b72fec95d3b95f92fb 100644
--- a/chrome/browser/ui/panels/panel_overflow_browsertest.cc
+++ b/chrome/browser/ui/panels/panel_overflow_browsertest.cc
@@ -250,10 +250,13 @@ IN_PROC_BROWSER_TEST_F(PanelOverflowBrowserTest, CheckPanelProperties) {
   EXPECT_EQ(Panel::USE_PANEL_ATTENTION, panel3->attention_mode());
   EXPECT_EQ(Panel::USE_PANEL_ATTENTION, panel4->attention_mode());
 
-  EXPECT_FALSE(panel1->CanResizeByMouse());
-  EXPECT_FALSE(panel2->CanResizeByMouse());
-  EXPECT_FALSE(panel3->CanResizeByMouse());
-  EXPECT_FALSE(panel4->CanResizeByMouse());
+  EXPECT_EQ(panel::RESIZABLE_ALL_SIDES_EXCEPT_BOTTOM,
+            panel1->CanResizeByMouse());
+  EXPECT_EQ(panel::RESIZABLE_ALL_SIDES_EXCEPT_BOTTOM,
+            panel2->CanResizeByMouse());
+  EXPECT_EQ(panel::RESIZABLE_ALL_SIDES_EXCEPT_BOTTOM,
+            panel3->CanResizeByMouse());
+  EXPECT_EQ(panel::NOT_RESIZABLE, panel4->CanResizeByMouse());
 
   // Make sure last panel really did overflow.
   WaitForLayoutModeChanged(panel4, PanelStrip::IN_OVERFLOW);