Refactor Telemetry value system to support AsDict()

tools/telemetry/telemetry/value/string.py

Index: tools/telemetry/telemetry/value/string.py
diff --git a/tools/telemetry/telemetry/value/string.py b/tools/telemetry/telemetry/value/string.py
index f413f8b8e95eb8a56bef9c0976339bcd5ece2bd8..9ca47f5a969e8dc533e989dc446a7b24cf0c4c42 100644
--- a/tools/telemetry/telemetry/value/string.py
+++ b/tools/telemetry/telemetry/value/string.py
@@ -45,6 +45,15 @@ class StringValue(value_module.Value):
     return str(self.value)
 
   @classmethod
+  def GetJSONTypeName(cls):
+    return 'string'
+
+  def AsDict(self):
+    d = super(StringValue, self).AsDict()
+    d['value'] = self.value
+    return d
+
+  @classmethod
   def MergeLikeValuesFromSamePage(cls, values):
     assert len(values) > 0
     v0 = values[0]