[MD History] Use proper shadows for cards.

chrome/browser/resources/md_history/shared_style.html

 <dom-module id="shared-style">
   <template>
     <style>
       :root {
         --card-border-color: rgba(0, 0, 0, 0.14);
         --card-first-last-item-padding: 8px;
         --card-max-width: 960px;
         --card-min-width: 550px;
         --card-padding-between: 20px;
         --card-padding-side: 24px;
         --card-sizing: {
           margin: 0 auto;
           max-width: var(--card-max-width);
           min-width: var(--card-min-width);
           padding: 0 var(--card-padding-side);
           width: calc(100% - 2 * var(--card-padding-side));
         };
+        --card-container-filter: {
+          filter: drop-shadow(0 2px 2px rgba(0, 0, 0, .05))

[tsergeant, 2016/08/05 00:16:48]

Maybe one day we'll be able to get the same shadows as everyone else:
https://bugs.chromium.org/p/chromium/issues/detail?id=610884

[calamity, 2016/08/05 04:01:58]

They don't even render the same T_T

Changed the badly performing pages to box shadow which match the downloads page,
but had to change the drop shadow to match. The same values result in different
shadows so I've eyeballed something that looks similar.

+              drop-shadow(0 1px 4px rgba(0, 0, 0, .08))
+              drop-shadow(0 1px 1px rgba(0, 0, 0, .2));
+        };
         --first-card-padding-top: 24px;
         --item-height: 44px;
         --primary-text-color: #333;
         --secondary-text-color: #757575;
         --side-bar-width: 256px;
         --toolbar-grouped-height: 101px;
         --toolbar-height: 56px;
       }
 
       [hidden] {
@@ skipping 34 matching lines @@
       .website-title {
         color: var(--primary-text-color);
         overflow: hidden;
         text-decoration: none;
         text-overflow: ellipsis;
         white-space: nowrap;
       }
     </style>
   </template>
 </dom-module>