changelog-webapp: All text fields required

This CL makes all text fields required.

BUG=b/160901711
TEST=run local

Change-Id: Ie3b3ddeaf8d7b01d4013dd31e16f797835ae59a2
diff --git a/src/cmd/changelog-webapp/static/templates/changelog.html b/src/cmd/changelog-webapp/static/templates/changelog.html
index 55b3e21..e5a3c3d 100644
--- a/src/cmd/changelog-webapp/static/templates/changelog.html
+++ b/src/cmd/changelog-webapp/static/templates/changelog.html
@@ -20,9 +20,9 @@
       <div class="text">
         <label>From </label>
         {{if (ne .Source "")}}
-          <input type="text" class="source" name="source" placeholder="COS build number" value={{.Source}} autocomplete="off">
+          <input type="text" class="source" name="source" placeholder="COS build number" value={{.Source}} autocomplete="off" required>
         {{else}}
-          <input type="text" class="source" name="source" placeholder="COS build number" autocomplete="off">
+          <input type="text" class="source" name="source" placeholder="COS build number" autocomplete="off" required>
         {{end}}
         <label> to </label>
         {{if (ne .Target "")}}
diff --git a/src/cmd/changelog-webapp/static/templates/locateBuild.html b/src/cmd/changelog-webapp/static/templates/locateBuild.html
index c2843f6..ca09a73 100644
--- a/src/cmd/changelog-webapp/static/templates/locateBuild.html
+++ b/src/cmd/changelog-webapp/static/templates/locateBuild.html
@@ -19,9 +19,9 @@
     <form class="changelog-form" action="/locatebuild">
       <div class="text">
         {{if (ne .CL "")}}
-          <input type="text" class="cl-input" name="cl" placeholder="CL-Number or Commit-SHA" value={{.CL}} autocomplete="off">
+          <input type="text" class="cl-input" name="cl" placeholder="CL-Number or Commit-SHA" value={{.CL}} autocomplete="off" required>
         {{else}}
-          <input type="text" class="cl-input" name="cl" placeholder="CL-Number or Commit-SHA" autocomplete="off">
+          <input type="text" class="cl-input" name="cl" placeholder="CL-Number or Commit-SHA" autocomplete="off" required>
         {{end}}
         <input class="submit" type="submit" value="Submit"><br>
       </div>