MD Downloads: remove bold selected item style

R=tsergeant@chromium.org
BUG=630619
CQ_INCLUDE_TRYBOTS=master.tryserver.chromium.linux:closure_compilation

Review-Url: https://codereview.chromium.org/2182863002
Cr-Commit-Position: refs/heads/master@{#407710}

chrome/browser/resources/md_downloads/toolbar.css

@@ -83,6 +83,12 @@ paper-icon-button {
   -webkit-margin-start: 16px;
 }
 
+paper-menu {
+  --paper-menu-selected-item: {
+    font-weight: normal;
+  };
+}
+
 paper-item {
   -webkit-user-select: none;
   cursor: pointer;

chrome/browser/resources/md_downloads/vulcanized.html

@@ -2582,6 +2582,12 @@ paper-icon-button {
   -webkit-margin-start: 16px;
 }
 
+paper-menu {
+  --paper-menu-selected-item: {
+    font-weight: normal;
+  };
+}
+
 paper-item {
   -webkit-user-select: none;
   cursor: pointer;