Use a scrollable tab strip on tablets at small widths

chrome/android/java/src/org/chromium/chrome/browser/compositor/overlays/strip/StripStacker.java

Index: chrome/android/java/src/org/chromium/chrome/browser/compositor/overlays/strip/StripStacker.java
diff --git a/chrome/android/java/src/org/chromium/chrome/browser/compositor/overlays/strip/StripStacker.java b/chrome/android/java/src/org/chromium/chrome/browser/compositor/overlays/strip/StripStacker.java
index 02e24cbeaf6ef130f96aa61597d8b9aff10c68bf..41968dde3f6b7fad82a7bbed27405266add60b46 100644
--- a/chrome/android/java/src/org/chromium/chrome/browser/compositor/overlays/strip/StripStacker.java
+++ b/chrome/android/java/src/org/chromium/chrome/browser/compositor/overlays/strip/StripStacker.java
@@ -5,43 +5,88 @@
 package org.chromium.chrome.browser.compositor.overlays.strip;
 
 import org.chromium.chrome.browser.compositor.layouts.Layout;
+import org.chromium.chrome.browser.util.MathUtils;
 
 /**
  * An interface that defines how to stack tabs and how they should look visually.  This lets
  * certain components customize how the {@link StripLayoutHelper} functions and how other
  * {@link Layout}s visually order tabs.
  */
-public interface StripStacker {
+public abstract class StripStacker {
     /**
      * @return Whether or not the close button can be shown.  Note that even if it can be shown,
      *         it might not be due to how much of the tab is actually visible to preserve proper hit
      *         target sizes.
      */
-    public boolean canShowCloseButton();
-
-    /**
-     * @return Whether or not the title text can slide to the right to stay visible.
-     */
-    public boolean canSlideTitleText();
+    public boolean canShowCloseButton() {
+        return true;
+    }
 
     /**
      * This gives the implementing class a chance to determine how the tabs should be ordered
-     * visually.  The positioning logic is the same regardless, this just has to do with visual
+     * visually. The positioning logic is the same regardless, this just has to do with visual
      * stacking.
      *
      * @param selectedIndex The selected index of the tabs.
      * @param indexOrderedTabs A list of tabs ordered by index.
-     * @param outVisualOrderedTabs The new list of tabs, ordered from back to front visually.
+     * @param outVisualOrderedTabs The new list of tabs, ordered from back (low z-index) to front
+     *                             (high z-index) visually.
      */
     public void createVisualOrdering(int selectedIndex, StripLayoutTab[] indexOrderedTabs,
-            StripLayoutTab[] outVisualOrderedTabs);
+            StripLayoutTab[] outVisualOrderedTabs) {
+        assert indexOrderedTabs.length == outVisualOrderedTabs.length;
+
+        selectedIndex = MathUtils.clamp(selectedIndex, 0, indexOrderedTabs.length);
+
+        int outIndex = 0;
+        for (int i = 0; i < selectedIndex; i++) {
+            outVisualOrderedTabs[outIndex++] = indexOrderedTabs[i];
+        }
+
+        for (int i = indexOrderedTabs.length - 1; i >= selectedIndex; --i) {
+            outVisualOrderedTabs[outIndex++] = indexOrderedTabs[i];
+        }
+    }
+
+    /**
+     * Computes and sets the draw X, draw Y, visibility and content offset for each tab.
+     *
+     * @param selectedIndex The selected index of the tabs.
+     * @param indexOrderedTabs A list of tabs ordered by index.
+     * @param tabStackWidth The width of a tab when it's stacked behind another tab.
+     * @param maxTabsToStack The maximum number of tabs to stack.
+     * @param tabOverlapWidth The amount tabs overlap.
+     * @param stripLeftMargin The left margin of the tab strip.
+     * @param stripRightMargin The right margin of the tab strip.
+     * @param stripWidth The width of the tab strip.
+     * @param inReorderMode Whether the strip is in reorder mode.
+     */
+    public abstract void setTabOffsets(int selectedIndex, StripLayoutTab[] indexOrderedTabs,
+            float tabStackWidth, int maxTabsToStack, float tabOverlapWidth, float stripLeftMargin,
+            float stripRightMargin, float stripWidth, boolean inReorderMode);
+
+    /**
+     * Computes the X offset for the new tab button.
+     *
+     * @param indexOrderedTabs A list of tabs ordered by index.
+     * @param tabOverlapWidth The amount tabs overlap.
+     * @param stripLeftMargin The left margin of the tab strip.
+     * @param stripRightMargin The right margin of the tab strip.
+     * @param stripWidth The width of the tab strip.
+     * @param mNewTabButtonWidth The width of the new tab button.
+     * @return The x offset for the new tab button.
+     */
+    public abstract float computeNewTabButtonOffset(StripLayoutTab[] indexOrderedTabs,
+            float tabOverlapWidth, float stripLeftMargin, float stripRightMargin, float stripWidth,
+            float mNewTabButtonWidth);
 
     /**
-     * Performs an occlusion pass, setting the visibility on tabs depending on whether or not they
-     * overlap each other perfectly.  This is relegated to this interface because the implementing
-     * class knows the proper visual order to optimize this pass.
+     * Performs an occlusion pass, setting the visibility on tabs. This is relegated to this
+     * interface because the implementing class knows the proper visual order to optimize this pass.
      * @param selectedIndex The selected index of the tabs.
      * @param indexOrderedTabs A list of tabs ordered by index.
+     * @param stripWidth The width of the tab strip.
      */
-    public void performOcclusionPass(int selectedIndex, StripLayoutTab[] indexOrderedTabs);
+    public abstract void performOcclusionPass(int selectedIndex, StripLayoutTab[] indexOrderedTabs,
+            float stripWidth);
 }