Plumb "enableSuperMixins" option through analysis server (implements DEP 34).

pkg/analysis_server/doc/api.html

Index: pkg/analysis_server/doc/api.html
diff --git a/pkg/analysis_server/doc/api.html b/pkg/analysis_server/doc/api.html
index 5fb468b0281ab990a8f9ea33c60985a816c663e9..717044822c694d8c9cffc1bb18d1ff2133860fa2 100644
--- a/pkg/analysis_server/doc/api.html
+++ b/pkg/analysis_server/doc/api.html
@@ -2379,6 +2379,12 @@ dt.typeDefinition {
               True if the client wants to enable support for the
               proposed "null aware operators" feature.
             </p>
+          </dd><dt class="field"><b><i>enableSuperMixins ( <span style="color:#999999">optional</span> bool )</i></b></dt><dd>
+            
+            <p>
+              True if the client wants to enable spport for the
+              proposed "less restricted mixins" proposal (DEP 34).
+            </p>
           </dd><dt class="field"><b><i>generateDart2jsHints ( <span style="color:#999999">optional</span> bool )</i></b></dt><dd>
             
             <p>