Bug 558108 - Reduce fuzzy page-fit-zoom threshold and make it a pref [r=mfinkle]

mobile/app/mobile.js

@@ -355,6 +355,9 @@ pref("browser.ui.kinetic.decelerationRate", 20);
 pref("browser.ui.kinetic.speedSensitivity", 80);
 pref("browser.ui.kinetic.swipeLength", 160);
 
+// zooming
+pref("browser.ui.zoom.pageFitGranularity", 10); // don't zoom to fit by less than 1/10.
+
 // Touch radius
 pref("browser.ui.touch.radius", 16);
 

mobile/chrome/content/BrowserView.js

@@ -46,7 +46,6 @@ const kBrowserFormZoomLevelMin = 1.0;
 const kBrowserFormZoomLevelMax = 2.0;
 const kBrowserViewZoomLevelPrecision = 10000;
 const kBrowserViewZoomLevelIncrement = 0.1;
-const kBrowserViewZoomLevelPageFitAdjust = 0.2;
 const kBrowserViewPrefetchBeginIdleWait = 1;    // seconds
 const kBrowserViewPrefetchBeginIdleWaitLoading = 10;    // seconds
 const kBrowserViewCacheSize = 6;
@@ -613,7 +612,8 @@ BrowserView.prototype = {
       return metaData.scale;
 
     let zl = this.getPageZoomLevel();
-    return BrowserView.Util.adjustZoomLevel(zl, kBrowserViewZoomLevelPageFitAdjust);
+    let granularity = gPrefService.getIntPref("browser.ui.zoom.pageFitGranularity");
+    return BrowserView.Util.adjustZoomLevel(zl, 1 / granularity);
   },
 
   getPageZoomLevel: function getPageZoomLevel() {