Step one towards stable error messages with details:

pkg/polymer/lib/src/build/log_injector.css

Index: pkg/polymer/lib/src/build/log_injector.css
diff --git a/pkg/polymer/lib/src/build/log_injector.css b/pkg/polymer/lib/src/build/log_injector.css
index c4a97055b0f71af1cbb7a3b90e2633559754ff77..e81eee4b3f0c303a711760261b17d9188226daee 100644
--- a/pkg/polymer/lib/src/build/log_injector.css
+++ b/pkg/polymer/lib/src/build/log_injector.css
@@ -5,7 +5,7 @@
   position: fixed;
   bottom: 0;
   right: 0;
-  max-width: 50vw;
+  max-width: 80vw;
   z-index: 10000;
   font-family: sans-serif !important;
 }
@@ -15,6 +15,8 @@
   color: white;
   border: solid 1px #666;
   border-bottom: 0px;
+  text-overflow: ellipsis;
+  overflow-x: hidden;
 }
 .build-logs .fine {
   color: green;
@@ -30,8 +32,6 @@
 }
 .build-logs .message {
   white-space: nowrap;
-  text-overflow: ellipsis;
-  overflow-x: hidden;
   cursor: pointer;
 }
 .build-logs .message.expanded {