Files app: Preview PDF file in fit-to-page mode in quick view.

Instead of using the default zoom level, we can set fit-to-zoom mode by default
to resize the preview automatically when Files app window is resized.

Bug: 809314
Test: Manually tested
Cq-Include-Trybots: master.tryserver.chromium.linux:closure_compilation
Change-Id: I6e8d2113c9bbbd65071de2191f4be37b62ef6fd0
Reviewed-on: https://chromium-review.googlesource.com/984912Reviewed-by: Tatsuhisa Yamaguchi <yamaguchi@chromium.org>
Commit-Queue: Naoki Fukino <fukino@chromium.org>
Cr-Commit-Position: refs/heads/master@{#548013}

ui/file_manager/file_manager/foreground/js/quick_view_controller.js

@@ -458,6 +458,8 @@ QuickViewController.prototype.getQuickViewParameters_ = function(
         });
         params.browsable = browsable;
         params.contentUrl = browsable ? URL.createObjectURL(file) : '';
+        if (params.subtype == 'PDF')
+          params.contentUrl += '#view=Fit';
         return params;
       }.bind(this))
       .catch(function(e) {