Make struct members nullable so demo_launcher no longer crashes.

This change fixes a few mojom declarations that were causing the
mojo_demo_launcher to crash when fetching a simple Apache "It works!"
web page.

Review URL: https://codereview.chromium.org/488263002

Cr-Commit-Position: refs/heads/master@{#291029}
git-svn-id: svn://svn.chromium.org/chrome/trunk/src@291029 0039d316-1c4b-4281-b951-d872f2087c98

mojo/services/public/interfaces/input_events/input_events.mojom

@@ -9,7 +9,7 @@ module mojo {
 
 struct LocationData {
   Point in_view_location;
-  Point screen_location;
+  Point? screen_location;
 };
 
 struct KeyData {

mojo/services/public/interfaces/network/url_loader.mojom

@@ -14,11 +14,11 @@ struct URLRequest {
   string method = "GET";
 
   // Additional HTTP request headers.
-  string[] headers;
+  string[]? headers;
 
   // The payload for the request body, represented as a concatenation of data
   // streams. For HTTP requests, the method must be set to "POST" or "PUT".
-  handle<data_pipe_consumer>[] body;
+  handle<data_pipe_consumer>[]? body;
 
   // The number of bytes to be read from |body|. A Content-Length header of
   // this value will be sent. Set to -1 if length is unknown, which will cause
@@ -43,7 +43,7 @@ struct URLRequest {
 
 struct URLResponse {
   // If the response resulted in a network level error, this field will be set.
-  NetworkError error;
+  NetworkError? error;
 
   // The response body stream. Read from this data pipe to receive the bytes of
   // response body.
@@ -70,14 +70,14 @@ struct URLResponse {
   // These fields are set to non-NULL if this response corresponds to a
   // redirect.  Call the |FollowRedirect| method on the URLLoader instance to
   // follow this redirect.
-  string redirect_method;
-  string redirect_url;
+  string? redirect_method;
+  string? redirect_url;
 };
 
 struct URLLoaderStatus {
   // If the loader has failed due to a network level error, this field will be
   // set.
-  NetworkError error;
+  NetworkError? error;
 
   // Set to true if the URLLoader is still working. Set to false once an error
   // is encountered or the response body is completely copied to the response