Refactor OverlayPanel height calculations

chrome/android/java/src/org/chromium/chrome/browser/compositor/bottombar/OverlayPanelBase.java

Index: chrome/android/java/src/org/chromium/chrome/browser/compositor/bottombar/OverlayPanelBase.java
diff --git a/chrome/android/java/src/org/chromium/chrome/browser/compositor/bottombar/OverlayPanelBase.java b/chrome/android/java/src/org/chromium/chrome/browser/compositor/bottombar/OverlayPanelBase.java
index 396cba5343ec60762335d572e25a6e0b512d0e28..6a0bf5a5598d363ba6ce9d0b0c8b375ecd3baf54 100644
--- a/chrome/android/java/src/org/chromium/chrome/browser/compositor/bottombar/OverlayPanelBase.java
+++ b/chrome/android/java/src/org/chromium/chrome/browser/compositor/bottombar/OverlayPanelBase.java
@@ -159,11 +159,6 @@ abstract class OverlayPanelBase {
     protected abstract void onClosed(StateChangeReason reason);
 
     /**
-     * @return The absolute amount in DP that the top controls have shifted off screen.
-     */
-    protected abstract float getTopControlsOffsetDp();
-
-    /**
      * TODO(mdjones): This method should be removed from this class.
      * @return The resource id that contains how large the top controls are.
      */
@@ -183,6 +178,7 @@ abstract class OverlayPanelBase {
 
     private float mLayoutWidth;
     private float mLayoutHeight;
+    private float mLayoutYOffset;
 
     private float mMaximumWidth;
     private float mMaximumHeight;
@@ -191,18 +187,23 @@ abstract class OverlayPanelBase {
     private boolean mOverrideIsFullWidthSizePanelForTesting;
 
     /**
-     * Called when the size of the view has changed.
+     * Called when the layout has changed.
      *
      * @param width  The new width in dp.
-     * @param height The new width in dp.
+     * @param height The new height in dp.
+     * @param visibleViewportOffsetY The Y offset of the content in dp.
      */
-    public void onSizeChanged(float width, float height) {
-        if (width == mLayoutWidth && height == mLayoutHeight) return;
+    public void onLayoutChanged(float width, float height, float visibleViewportOffsetY) {
+        if (width == mLayoutWidth && height == mLayoutHeight
+                && visibleViewportOffsetY == mLayoutYOffset) {
+            return;
+        }
 
         float previousLayoutWidth = mLayoutWidth;
 
         mLayoutWidth = width;
         mLayoutHeight = height;
+        mLayoutYOffset = visibleViewportOffsetY;
 
         mMaximumWidth = calculateOverlayPanelWidth();
         mMaximumHeight = getPanelHeightFromState(PanelState.MAXIMIZED);
@@ -258,14 +259,6 @@ abstract class OverlayPanelBase {
     }
 
     /**
-     * @param y The y coordinate.
-     * @return The Y coordinate relative the fullscreen height.
-     */
-    public float getFullscreenY(float y) {
-        return y + (mToolbarHeight - getTopControlsOffsetDp()) / mPxToDp;
-    }
-
-    /**
      * @return Whether the Panel is showing.
      */
     public boolean isShowing() {
@@ -291,9 +284,7 @@ abstract class OverlayPanelBase {
      * @return The height of the tab the panel is displayed on top of.
      */
     public float getTabHeight() {
-        // NOTE(mdjones): This value will always be the same for a particular orientation; it is
-        // the content height + visible toolbar height.
-        return mLayoutHeight + (getToolbarHeight() - getTopControlsOffsetDp());
+        return mLayoutHeight;
     }
 
     /**
@@ -1099,15 +1090,10 @@ abstract class OverlayPanelBase {
         // always return zero to ensure the Base Page remains in the same position.
         if (!isFullWidthSizePanel()) return 0.f;
 
-        // Start with the desired offset.
-        float offset = calculateBasePageDesiredOffset();
+        // Start with the desired offset taking viewport offset into consideration and make sure
+        // the result is <= 0 so the page moves up and not down.
+        float offset = Math.min(calculateBasePageDesiredOffset() - mLayoutYOffset, 0.0f);
 
-        // Make sure offset is negative to prevent Base Page from moving down,
-        // because there's nothing to render above the Page.
-        offset = Math.min(offset, 0.f);
-        // If visible, the Toolbar will be hidden. Therefore, we need to adjust
-        // the offset to account for this difference.
-        offset -= (mToolbarHeight - getTopControlsOffsetDp());
         // Make sure the offset is not greater than the expanded height, because
         // there's nothing to render below the Page.
         offset = Math.max(offset, -getExpandedHeight());