DevTools: Add test for SourceCodeDiff

third_party/WebKit/LayoutTests/inspector/sources/resources/diff-after.css

Index: third_party/WebKit/LayoutTests/inspector/sources/resources/diff-after.css
diff --git a/third_party/WebKit/LayoutTests/inspector/sources/resources/diff-after.css b/third_party/WebKit/LayoutTests/inspector/sources/resources/diff-after.css
new file mode 100644
index 0000000000000000000000000000000000000000..77e421dc7aa491ffc95aa9d2f6581260629d460d
--- /dev/null
+++ b/third_party/WebKit/LayoutTests/inspector/sources/resources/diff-after.css
@@ -0,0 +1,29 @@
+.stays-the-same {
+    font-size: 10px;
+    font-family: sans-serif;
+}
+
+.was-modified {
+    width: 0%;
+}
+
+.stays-the-same2 {
+    font-size: 10px;
+    font-family: Arial, Helvetica, sans-serif;
+}
+
+.was-added {
+    color: #00F;
+    color: #008;
+    color: #000;
+}
+
+.stays-the-same3 {
+    font-size: 15px;
+    font-family: Arial, Helvetica, sans-serif;
+}
+
+.will-lose-properties {
+    background: #000;
+    background: #F00;
+}