MD Downloads: add first meaningful paint metrics to UMA

chrome/browser/resources/md_history/lazy_load.vulcanized.html

Index: chrome/browser/resources/md_history/lazy_load.vulcanized.html
diff --git a/chrome/browser/resources/md_history/lazy_load.vulcanized.html b/chrome/browser/resources/md_history/lazy_load.vulcanized.html
index 23ee2097ea9a172744681fcb7573acfa4e56cc20..d305c9e20f6107e7c7cc9520d10b26699e5df72b 100644
--- a/chrome/browser/resources/md_history/lazy_load.vulcanized.html
+++ b/chrome/browser/resources/md_history/lazy_load.vulcanized.html
@@ -900,6 +900,36 @@ paper-spinner {
   cursor: var(--cr-actionable_-_cursor);
 }
 
+button[is='paper-icon-button-light'] {
+  -webkit-margin-end: var(--cr-paper-icon-button-margin_-_-webkit-margin-end); -webkit-margin-start: var(--cr-paper-icon-button-margin_-_-webkit-margin-start);
+        background-position: center;
+        background-repeat: no-repeat;
+        background-size: var(--cr-icon-size);
+        flex-shrink: 0;
+        height: var(--cr-icon-ripple-size);
+        width: var(--cr-icon-ripple-size);
+}
+
+button[is='paper-icon-button-light'].subpage-arrow {
+  background-image: url("chrome://resources/images/arrow_right.svg");
+}
+
+button[is='paper-icon-button-light'].icon-external {
+  background-image: url("chrome://resources/images/open_in_new.svg");
+}
+
+.subpage-arrow, .icon-external {
+  display: none;
+}
+
+paper-icon-button.subpage-arrow {
+  background-image: url("chrome://resources/images/arrow_right.svg");
+}
+
+[actionable] :-webkit-any(.subpage-arrow, .icon-external), [actionable]:-webkit-any(.subpage-arrow, .icon-external) {
+  display: block;
+}
+
 [scrollable] {
   border-color: transparent;
         border-style: solid;
@@ -1434,4 +1464,4 @@ paper-icon-button {
   </template>
 
   </dom-module>
-</div><script src="lazy_load.crisper.js"></script></body></html>
+</div><script src="lazy_load.crisper.js"></script></body></html>