[android] Un-delete zoom APIs.

The Zoom APIs are still needed, so partially reverting r227763.

R=joth@chromium.org, qinmin@chromium.org
TBR=joth@chromium.org

BUG=None
TEST=None

Review URL: https://codereview.chromium.org/26737002

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@227793 0039d316-1c4b-4281-b951-d872f2087c98

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

@@ -650,7 +650,42 @@ public boolean isCrashed() {
     }
 
     /**
-     * Return the current scale.
+     * Zooms in the WebView by 25% (or less if that would result in zooming in
+     * more than possible).
+     *
+     * @return True if there was a zoom change, false otherwise.
+     */
+    // This method uses the term 'zoom' for legacy reasons, but relates
+    // to what chrome calls the 'page scale factor'.
+    public boolean zoomIn() {
+        return mContentViewCore.zoomIn();
+    }
+
+    /**
+     * Zooms out the WebView by 20% (or less if that would result in zooming out
+     * more than possible).
+     *
+     * @return True if there was a zoom change, false otherwise.
+     */
+    // This method uses the term 'zoom' for legacy reasons, but relates
+    // to what chrome calls the 'page scale factor'.
+    public boolean zoomOut() {
+        return mContentViewCore.zoomOut();
+    }
+
+    /**
+     * Resets the zoom factor of the WebView.
+     *
+     * @return True if there was a zoom change, false otherwise.
+     */
+    // This method uses the term 'zoom' for legacy reasons, but relates
+    // to what chrome calls the 'page scale factor'.
+    public boolean zoomReset() {
+        return mContentViewCore.zoomReset();
+    }
+
+    /**
+     * Return the current scale of the WebView
      * @return The current scale.
      */
     public float getScale() {

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

@@ -100,6 +100,10 @@ public class ContentViewCore implements MotionEventDelegate,
 
     private static final String TAG = "ContentViewCore";
 
+    // Used to avoid enabling zooming in / out if resulting zooming will
+    // produce little visible difference.
+    private static final float ZOOM_CONTROLS_EPSILON = 0.007f;
+
     // Used to represent gestures for long press and long tap.
     private static final int IS_LONG_PRESS = 1;
     private static final int IS_LONG_TAP = 2;
@@ -2574,11 +2578,82 @@ public boolean hasFocus() {
         return mContainerView.hasFocus();
     }
 
+    /**
+     * Checks whether the ContentViewCore can be zoomed in.
+     *
+     * @return True if the ContentViewCore can be zoomed in.
+     */
+    // This method uses the term 'zoom' for legacy reasons, but relates
+    // to what chrome calls the 'page scale factor'.
+    public boolean canZoomIn() {
+        final float zoomInExtent = mRenderCoordinates.getMaxPageScaleFactor()
+                - mRenderCoordinates.getPageScaleFactor();
+        return zoomInExtent > ZOOM_CONTROLS_EPSILON;
+    }
+
+    /**
+     * Checks whether the ContentViewCore can be zoomed out.
+     *
+     * @return True if the ContentViewCore can be zoomed out.
+     */
+    // This method uses the term 'zoom' for legacy reasons, but relates
+    // to what chrome calls the 'page scale factor'.
+    public boolean canZoomOut() {
+        final float zoomOutExtent = mRenderCoordinates.getPageScaleFactor()
+                - mRenderCoordinates.getMinPageScaleFactor();
+        return zoomOutExtent > ZOOM_CONTROLS_EPSILON;
+    }
+
+    /**
+     * Zooms in the ContentViewCore by 25% (or less if that would result in
+     * zooming in more than possible).
+     *
+     * @return True if there was a zoom change, false otherwise.
+     */
+    // This method uses the term 'zoom' for legacy reasons, but relates
+    // to what chrome calls the 'page scale factor'.
+    public boolean zoomIn() {
+        if (!canZoomIn()) {
+            return false;
+        }
+        return pinchByDelta(1.25f);
+    }
+
+    /**
+     * Zooms out the ContentViewCore by 20% (or less if that would result in
+     * zooming out more than possible).
+     *
+     * @return True if there was a zoom change, false otherwise.
+     */
+    // This method uses the term 'zoom' for legacy reasons, but relates
+    // to what chrome calls the 'page scale factor'.
+    public boolean zoomOut() {
+        if (!canZoomOut()) {
+            return false;
+        }
+        return pinchByDelta(0.8f);
+    }
+
+    /**
+     * Resets the zoom factor of the ContentViewCore.
+     *
+     * @return True if there was a zoom change, false otherwise.
+     */
+    // This method uses the term 'zoom' for legacy reasons, but relates
+    // to what chrome calls the 'page scale factor'.
+    public boolean zoomReset() {
+        // The page scale factor is initialized to mNativeMinimumScale when
+        // the page finishes loading. Thus sets it back to mNativeMinimumScale.
+        if (!canZoomOut()) return false;
+        return pinchByDelta(
+                mRenderCoordinates.getMinPageScaleFactor()
+                        / mRenderCoordinates.getPageScaleFactor());
+    }
+
     /**
      * Simulate a pinch zoom gesture.
      *
      * @param delta the factor by which the current page scale should be multiplied by.
-     *
      * @return whether the gesture was sent.
      */
     public boolean pinchByDelta(float delta) {