Material PDF: Improve layout of PDF viewer in very small windows

chrome/browser/resources/pdf/elements/viewer-pdf-toolbar/viewer-pdf-toolbar.css

Index: chrome/browser/resources/pdf/elements/viewer-pdf-toolbar/viewer-pdf-toolbar.css
diff --git a/chrome/browser/resources/pdf/elements/viewer-pdf-toolbar/viewer-pdf-toolbar.css b/chrome/browser/resources/pdf/elements/viewer-pdf-toolbar/viewer-pdf-toolbar.css
index 0cab638e25530dfa7647df2726ef18fe8e0d37dd..08336d0ffcefcd4eae6aa456f954502a43be3ac8 100644
--- a/chrome/browser/resources/pdf/elements/viewer-pdf-toolbar/viewer-pdf-toolbar.css
+++ b/chrome/browser/resources/pdf/elements/viewer-pdf-toolbar/viewer-pdf-toolbar.css
@@ -65,3 +65,27 @@ paper-toolbar /deep/ .toolbar-tools {
 .invisible {
   visibility: hidden;
 }
+
+@media(max-width: 675px) {
+  #bookmarks,
+  #rotate-left {
+    display: none;
+  }
+
+  #pageselector-container {
+    flex: 2;
+  }
+}
+
+@media(max-width: 450px) {
+  #rotate-right {
+    display: none;
+  }
+}
+
+@media(max-width: 400px) {
+  #buttons,
+  #pageselector-container {
+    display: none;
+  }
+}