Use WindowAndroid to get display metrics in ContentViewCore

content/public/android/java/src/org/chromium/content/browser/RenderCoordinates.java

Index: content/public/android/java/src/org/chromium/content/browser/RenderCoordinates.java
diff --git a/content/public/android/java/src/org/chromium/content/browser/RenderCoordinates.java b/content/public/android/java/src/org/chromium/content/browser/RenderCoordinates.java
index a971c681ec145ef91c1fa6ef92aeb96a5fb4a90a..2df4f974938fc00b0ed8930b8fab2d0c6fdca053 100644
--- a/content/public/android/java/src/org/chromium/content/browser/RenderCoordinates.java
+++ b/content/public/android/java/src/org/chromium/content/browser/RenderCoordinates.java
@@ -4,7 +4,12 @@
 
 package org.chromium.content.browser;
 
+import android.content.Context;
+import android.util.TypedValue;
+
+import org.chromium.base.CommandLine;
 import org.chromium.base.VisibleForTesting;
+import org.chromium.content.common.ContentSwitches;
 
 /**
  * Cached copy of all positions and scales (CSS-to-DIP-to-physical pixels)
@@ -36,6 +41,10 @@ public class RenderCoordinates {
     // Cached device density.
     private float mDeviceScaleFactor;
 
+    // Multiplier that determines how many (device) pixels to scroll per mouse
+    // wheel tick. Defaults to the preferred list item height.
+    private float mWheelScrollFactor;
+
     private float mTopContentOffsetYPix;
     private float mBottomContentOffsetYPix;
 
@@ -53,8 +62,27 @@ public class RenderCoordinates {
         mContentHeightCss = contentHeightCss;
     }
 
-    void setDeviceScaleFactor(float deviceScaleFactor) {
-        mDeviceScaleFactor = deviceScaleFactor;
+    void setDeviceScaleFactor(Context context) {
+        String forceScaleFactor =
+                CommandLine.getInstance().getSwitchValue(ContentSwitches.FORCE_DEVICE_SCALE_FACTOR);
+        mDeviceScaleFactor = forceScaleFactor != null
+                ? Float.valueOf(forceScaleFactor)
+                : context.getResources().getDisplayMetrics().density;
+
+        // The wheel scroll factor depends on the theme in the context.
+        // This code assumes that the theme won't change between this call and
+        // getWheelScrollScale().
+
+        TypedValue outValue = new TypedValue();
+        // This is the same attribute used by Android Views to scale wheel
+        // event motion into scroll deltas.
+        if (context.getTheme().resolveAttribute(
+                    android.R.attr.listPreferredItemHeight, outValue, true)) {
+            mWheelScrollFactor = outValue.getDimension(context.getResources().getDisplayMetrics());
+        } else {
+            // If attribute retrieval fails, just use a sensible default.
+            mWheelScrollFactor = 64 * mDeviceScaleFactor;
+        }
     }
 
     void updateFrameInfo(
@@ -343,6 +371,13 @@ public class RenderCoordinates {
     }
 
     /**
+     * @return Current wheel scroll factor (physical pixels per mouse scroll click).
+     */
+    public float getWheelScrollFactor() {
+        return mWheelScrollFactor;
+    }
+
+    /**
      * @return Maximum possible horizontal scroll in physical pixels.
      */
     public float getMaxHorizontalScrollPix() {