modularize the display of diffs for skpdiff

R=djsollen@google.com

Review URL: https://codereview.chromium.org/18925004

git-svn-id: http://skia.googlecode.com/svn/trunk@10044 2bbb7eff-a529-9590-31e7-b0007b416f81
diff --git a/experimental/skpdiff/viewer_style.css b/experimental/skpdiff/viewer_style.css
index 48a295c..140deaa 100644
--- a/experimental/skpdiff/viewer_style.css
+++ b/experimental/skpdiff/viewer_style.css
@@ -20,14 +20,18 @@
 }
 
 .gm-image {
-    width:300px;
+    border: 1px dotted black;
 }
 
-.baseline-image {
+.gm-image:hover {
+    border: 1px dashed black;
+}
+
+.left-image {
     float: right;
 }
 
-.test-image {
+.right-image {
     text-align: right;
 }