Change zoom presets to be more useful.

components/zoom/page_zoom_constants.cc

Index: components/zoom/page_zoom_constants.cc
diff --git a/components/zoom/page_zoom_constants.cc b/components/zoom/page_zoom_constants.cc
index 55bc6d2485e6be3d0bb5630d75b2016eea1e665c..5c8dacec67d2093b2bdc0967dd11741dc4a03aff 100644
--- a/components/zoom/page_zoom_constants.cc
+++ b/components/zoom/page_zoom_constants.cc
@@ -10,9 +10,9 @@ namespace zoom {
 
 // This list is duplicated in chrome/browser/resources/pdf/viewport.js. Please
 // make sure the two match.
-const double kPresetZoomFactors[] = {0.25, 0.333, 0.5,  0.666, 0.75, 0.9,
-                                     1.0,  1.1,   1.25, 1.5,   1.75, 2.0,
-                                     2.5,  3.0,   4.0,  5.0};
+const double kPresetZoomFactors[] = {0.25, 1 / 3.0, 0.5, 2 / 3.0, 0.75, 0.8,
+                                     0.9, 1.0, 1.1, 1.25, 1.5, 1.75, 2.0, 2.5,
+                                     3.0, 4.0, 5.0};
 const std::size_t kPresetZoomFactorsSize = arraysize(kPresetZoomFactors);
 
 }  // namespace ui_zoom