Teach tools/skydb how to take a URL as a parameter.

sky/tools/debugger/prompt/prompt.cc

Index: sky/tools/debugger/prompt/prompt.cc
diff --git a/sky/tools/debugger/prompt/prompt.cc b/sky/tools/debugger/prompt/prompt.cc
index 60d6733802f31c156be09225ce2f4818fcbf6e59..3b486045e6d9de4f6cb56057d794b72005721b1e 100644
--- a/sky/tools/debugger/prompt/prompt.cc
+++ b/sky/tools/debugger/prompt/prompt.cc
@@ -43,12 +43,16 @@ class Prompt : public mojo::ApplicationDelegate {
   // Overridden from mojo::ApplicationDelegate:
   virtual void Initialize(mojo::ApplicationImpl* app) override {
     app->ConnectToService("mojo:sky_viewer", &tracing_);
-    ScheduleWaitForInput();
+    if (app->args().size() > 1)
+      url_ = app->args()[1];
   }
 
   virtual bool ConfigureIncomingConnection(
       mojo::ApplicationConnection* connection) override {
     connection->ConnectToService(&debugger_);
+    if (!url_.empty())
+      Reload();
+    ScheduleWaitForInput();
     return true;
   }