Update computation of reading level scale.

Fixes bug 5726043 (Extra double-tap needed to zoom out to overview mode
on nytimes.com on a Stingray)

Change-Id: I54dc303f4aa81ddc38c234228adc915b9f6749dc

core/java/android/webkit/WebView.java

@@ -2496,11 +2496,12 @@ public class WebView extends AbsoluteLayout
     }
 
     /**
-     * Return the reading level scale of the WebView
+     * Compute the reading level scale of the WebView
+     * @param scale The current scale.
      * @return The reading level scale.
      */
-    /*package*/ float getReadingLevelScale() {
-        return mZoomManager.getReadingLevelScale();
+    /*package*/ float computeReadingLevelScale(float scale) {
+        return mZoomManager.computeReadingLevelScale(scale);
     }
 
     /**

core/java/android/webkit/WebViewCore.java

@@ -2514,7 +2514,7 @@ public final class WebViewCore {
                     if (mSettings.isNarrowColumnLayout()) {
                         // In case of automatic text reflow in fixed view port mode.
                         mInitialViewState.mTextWrapScale =
-                                mWebView.getReadingLevelScale();
+                                mWebView.computeReadingLevelScale(data.mScale);
                     }
                 } else {
                     // Scale is given such as when page is restored, use it.

core/java/android/webkit/ZoomManager.java

@@ -316,7 +316,12 @@ class ZoomManager {
      * Returns the zoom scale used for reading text on a double-tap.
      */
     public final float getReadingLevelScale() {
-        return mDisplayDensity * mDoubleTapZoomFactor;
+        return computeScaleWithLimits(computeReadingLevelScale(getZoomOverviewScale()));
+    }
+
+    /* package */ final float computeReadingLevelScale(float scale) {
+        return Math.max(mDisplayDensity * mDoubleTapZoomFactor,
+                scale + MIN_DOUBLE_TAP_SCALE_INCREMENT);
     }
 
     public final float getInvDefaultScale() {
@@ -678,7 +683,7 @@ class ZoomManager {
             }
             zoomToOverview();
         } else {
-            zoomToReadingLevelOrMore();
+            zoomToReadingLevel();
         }
     }
 
@@ -709,9 +714,8 @@ class ZoomManager {
             !mWebView.getSettings().getUseFixedViewport());
     }
 
-    private void zoomToReadingLevelOrMore() {
-        final float zoomScale = Math.max(getReadingLevelScale(),
-                mActualScale + MIN_DOUBLE_TAP_SCALE_INCREMENT);
+    private void zoomToReadingLevel() {
+        final float readingScale = getReadingLevelScale();
 
         int left = mWebView.nativeGetBlockLeftEdge(mAnchorX, mAnchorY, mActualScale);
         if (left != WebView.NO_LEFTEDGE) {
@@ -721,13 +725,13 @@ class ZoomManager {
             // Re-calculate the zoom center so that the new scroll x will be
             // on the left edge.
             if (viewLeft > 0) {
-                mZoomCenterX = viewLeft * zoomScale / (zoomScale - mActualScale);
+                mZoomCenterX = viewLeft * readingScale / (readingScale - mActualScale);
             } else {
                 mWebView.scrollBy(viewLeft, 0);
                 mZoomCenterX = 0;
             }
         }
-        startZoomAnimation(zoomScale,
+        startZoomAnimation(readingScale,
             !mWebView.getSettings().getUseFixedViewport());
     }