Reland "[Tab Scrolling] Add test for tabstrip resizing when dragging."

This reverts commit 2c73aa66.

Reason for revert: Disabling test on linux
Original change's description:
> Revert "[Tab Scrolling] Add test for tabstrip resizing when dragging."
>
> This reverts commit a4b670d5.
>
> Reason for revert: Test is flaky/failing on https://ci.chromium.org/p/chromium/builders/ci/Linux%20Tests
>
> https://ci.chromium.org/p/chromium/builders/ci/Linux%20Tests/95514?
>
> ../../chrome/browser/ui/views/tabs/tab_drag_controller_interactive_uitest.cc:2470: Failure
> Expected equality of these values:
>   tab_strip_width + TabStyle::GetStandardWidth()
>     Which is: 751
>   tab_strip->width()
>     Which is: 761
>
> Original change's description:
> > [Tab Scrolling] Add test for tabstrip resizing when dragging.
> >
> > When the browser window is large enough, the tabstrip should expand to
> > accommodate tabs dragging past the last tab. This is a test for
> > crrev.com/c/2472577
> >
> > Bug: 1141674
> > Change-Id: Icfb4b0d6b9ebfa243a0e352b0cef68a2a6f2c263
> > Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2537068
> > Reviewed-by: Taylor Bergquist <tbergquist@chromium.org>
> > Commit-Queue: Charlene Yan <cyan@chromium.org>
> > Cr-Commit-Position: refs/heads/master@{#827998}
>
> TBR=tbergquist@chromium.org,cyan@chromium.org
>
> Change-Id: Iaee8c99d3a53eb4f1031d969b01e39d86febe6a3
> No-Presubmit: true
> No-Tree-Checks: true
> No-Try: true
> Bug: 1141674
> Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2545744
> Reviewed-by: Marijn Kruisselbrink <mek@chromium.org>
> Commit-Queue: Marijn Kruisselbrink <mek@chromium.org>
> Cr-Commit-Position: refs/heads/master@{#828425}

TBR=mek@chromium.org,tbergquist@chromium.org,cyan@chromium.org

# Not skipping CQ checks because original CL landed > 1 day ago.

Bug: 1141674
Change-Id: If7b71337950554f49dc9d635dbb2a2a35f0c280c
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2559577Reviewed-by: Charlene Yan <cyan@chromium.org>
Commit-Queue: Charlene Yan <cyan@chromium.org>
Cr-Commit-Position: refs/heads/master@{#831141}

chrome/browser/ui/views/tabs/tab_drag_controller_interactive_uitest.cc

@@ -37,6 +37,7 @@
 #include "chrome/browser/ui/tabs/tab_group.h"
 #include "chrome/browser/ui/tabs/tab_group_model.h"
 #include "chrome/browser/ui/tabs/tab_strip_model.h"
+#include "chrome/browser/ui/tabs/tab_style.h"
 #include "chrome/browser/ui/ui_features.h"
 #include "chrome/browser/ui/views/frame/browser_view.h"
 #include "chrome/browser/ui/views/frame/native_browser_frame_factory.h"
@@ -2447,6 +2448,48 @@ IN_PROC_BROWSER_TEST_P(
   EXPECT_EQ(browser2_groups[0], group);
 }
 
+class DetachToBrowserTabDragControllerTestWithScrollableTabStripEnabled
+    : public DetachToBrowserTabDragControllerTest {
+ public:
+  DetachToBrowserTabDragControllerTestWithScrollableTabStripEnabled() {
+    scoped_feature_list_.InitWithFeatures({features::kScrollableTabStrip}, {});
+  }
+
+ private:
+  base::test::ScopedFeatureList scoped_feature_list_;
+};
+
+#if defined(OS_LINUX)
+#define MAYBE_DraggingRightExpandsTabStripSize \
+  DISABLED_DraggingRightExpandsTabStripSize
+#else
+#define MAYBE_DraggingRightExpandsTabStripSize DraggingRightExpandsTabStripSize
+#endif
+// Creates a browser with two tabs and drags the rightmost tab. Given the
+// browser window is large enough, the tabstrip should expand to accommodate
+// this tab. Note: There must be at least two tabs because dragging a singular
+// tab will drag the window.
+// Disabled for Linux due to test dragging flakiness.
+IN_PROC_BROWSER_TEST_P(
+    DetachToBrowserTabDragControllerTestWithScrollableTabStripEnabled,
+    MAYBE_DraggingRightExpandsTabStripSize) {
+  TabStrip* tab_strip = GetTabStripForBrowser(browser());
+
+  AddTabsAndResetBrowser(browser(), 1);
+
+  browser()->window()->SetBounds(
+      gfx::Rect(0, 0, TabStyle::GetStandardWidth() * 4, 400));
+
+  const int tab_strip_width = tab_strip->width();
+  const gfx::Point tab_1_center =
+      GetCenterInScreenCoordinates(tab_strip->tab_at(1));
+  ASSERT_TRUE(PressInput(tab_1_center));
+  ASSERT_TRUE(DragInputTo(tab_1_center +
+                          gfx::Vector2d(TabStyle::GetStandardWidth(), 0)));
+  EXPECT_EQ(tab_strip_width + TabStyle::GetStandardWidth(), tab_strip->width());
+  ASSERT_TRUE(ReleaseInput());
+}
+
 namespace {
 
 // Invoked from the nested run loop.
@@ -4369,6 +4412,10 @@ INSTANTIATE_TEST_SUITE_P(
     TabDragging,
     DetachToBrowserTabDragControllerTestWithTabGroupsCollapseEnabled,
     ::testing::Values("mouse", "touch"));
+INSTANTIATE_TEST_SUITE_P(
+    TabDragging,
+    DetachToBrowserTabDragControllerTestWithScrollableTabStripEnabled,
+    ::testing::Values("mouse", "touch"));
 INSTANTIATE_TEST_SUITE_P(TabDragging,
                          DetachToBrowserInSeparateDisplayTabDragControllerTest,
                          ::testing::Values("mouse"));
@@ -4394,4 +4441,8 @@ INSTANTIATE_TEST_SUITE_P(
     TabDragging,
     DetachToBrowserTabDragControllerTestWithTabGroupsCollapseEnabled,
     ::testing::Values("mouse"));
+INSTANTIATE_TEST_SUITE_P(
+    TabDragging,
+    DetachToBrowserTabDragControllerTestWithScrollableTabStripEnabled,
+    ::testing::Values("mouse"));
 #endif