OOP PDF - Update zoom factor to fall within range

Currently setZoom() doesn't check whether zoom factor provided
falls within range or not. It is possible to pass big zoom level
through 'zoom' open pdf parameter which can make browser unresponsive.

This patch updates the zoom factor provided in setZoom() to fall
within range.

BUG=303491

Review URL: https://codereview.chromium.org/475933004

Cr-Commit-Position: refs/heads/master@{#291387}
git-svn-id: svn://svn.chromium.org/chrome/trunk/src@291387 0039d316-1c4b-4281-b951-d872f2087c98

chrome/browser/resources/pdf/viewport.js

@@ -76,6 +76,14 @@ Viewport.SCROLL_INCREMENT = 40;
 Viewport.ZOOM_FACTORS = [0.25, 0.333, 0.5, 0.666, 0.75, 0.9, 1,
                          1.1, 1.25, 1.5, 1.75, 2, 2.5, 3, 4, 5];
 
+/**
+ * The minimum and maximum range to be used to clip zoom factor.
+ */
+Viewport.ZOOM_FACTOR_RANGE = {
+  min: Viewport.ZOOM_FACTORS[0],
+  max: Viewport.ZOOM_FACTORS[Viewport.ZOOM_FACTORS.length - 1]
+};
+
 /**
  * The width of the page shadow around pages in pixels.
  */
@@ -231,6 +239,8 @@ Viewport.prototype = {
    * @param {number} newZoom the zoom level to zoom to.
    */
   setZoom: function(newZoom) {
+    newZoom = Math.max(Viewport.ZOOM_FACTOR_RANGE.min,
+                       Math.min(newZoom, Viewport.ZOOM_FACTOR_RANGE.max));
     this.mightZoom_(function() {
       this.setZoomInternal_(newZoom);
       this.updateViewport_();