[MD settings] OnStartup settings layout closer to mocks

chrome/browser/resources/settings/settings_dialog.css

Index: chrome/browser/resources/settings/settings_dialog.css
diff --git a/chrome/browser/resources/settings/settings_dialog.css b/chrome/browser/resources/settings/settings_dialog.css
index f868244eaf6d680e775b5b3cf4fde8b48a951da7..bdbfbc86e2193ad49c58758a6f3f841417ef2773 100644
--- a/chrome/browser/resources/settings/settings_dialog.css
+++ b/chrome/browser/resources/settings/settings_dialog.css
@@ -28,6 +28,8 @@ paper-dialog .title {
 }
 
 paper-dialog .body {
+  display: flex;
+  flex-flow: column;
   font-size: 1em;
   margin: 20px 0;
 }
@@ -51,12 +53,12 @@ paper-dialog .cancel-button {
 }
 
 paper-dialog .explanation {
+  flex: 1;

[dpapad, 2016/01/12 00:43:47]

As discussed in person, it looks better to me to remove the flex:1 from here and
also remove the min-height from the "Add a page" dialog.

[dschuyler, 2016/01/12 19:49:37]

I like those suggestions.  I've asked Alan for his thoughts.
I'm going to make these changes for now and make adjustments
later if Alan would like the layout done differently. 

   margin-bottom: 35px;
 }
 
 paper-dialog .button-container {
   display: flex;
-  flex: 1;
   justify-content: flex-end;
 }