Add package root setting to analysis server API.

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 598a9e6aa29a853621da114beced1147e2a9e1ee..2b322815f8481810cc0563036646a91f062162b1 100644
--- a/pkg/analysis_server/doc/api.html
+++ b/pkg/analysis_server/doc/api.html
@@ -451,6 +451,7 @@ dt.typeDefinition {
   "params": {
     "<b>included</b>": List&lt;<a href="#type_FilePath">FilePath</a>&gt;
     "<b>excluded</b>": List&lt;<a href="#type_FilePath">FilePath</a>&gt;
+    "<b>packageRoots</b>": <span style="color:#999999">optional</span> Map&lt;<a href="#type_FilePath">FilePath</a>, <a href="#type_FilePath">FilePath</a>&gt;
   }
 }</pre><br><pre>response: {
   "id": String
@@ -498,6 +499,24 @@ dt.typeDefinition {
               A list of the files and directories within the
               included directories that should not be analyzed.
             </p>
+          </dd><dt class="field"><b><i>packageRoots ( <span style="color:#999999">optional</span> Map&lt;<a href="#type_FilePath">FilePath</a>, <a href="#type_FilePath">FilePath</a>&gt; )</i></b></dt><dd>
+            
+            <p>
+              A mapping from source directories to target directories
+              that should override the normal package: URI resolution
+              mechanism.  The analyzer will behave as though each
+              source directory in the map contains a special
+              pubspec.yaml file which resolves any package: URI to the
+              corresponding path within the target directory.  The
+              effect is the same as specifying the target directory as
+              a "--package_root" parameter to the Dart VM when
+              executing any Dart file inside the source directory.
+            </p>
+            <p>
+              If this field is absent, or the empty map is specified,
+              then all package: URI's are resolved the normal
+              pubspec.yaml mechanism.
+            </p>
           </dd></dl></dd><dt class="request">analysis.setPriorityFiles</dt><dd><div class="box"><pre>request: {
   "id": String
   "method": "analysis.setPriorityFiles"