Change the "sleep" support to not block a thread.

This should help with some things that do multiple fetches at a time as we were
stalling all connections.

UnitTests/GTMHTTPServer.h

@@ -114,6 +114,9 @@ enum {
 @property(nonatomic, readonly) int statusCode;
 @property(nonatomic, copy) NSData *body;
 
+// If non zero, the response will be queued tobe sent after this amount of time.
+@property(nonatomic) double delaySeconds;
+
 + (instancetype)responseWithString:(NSString *)plainText;
 + (instancetype)responseWithHTMLString:(NSString *)htmlString;
 + (instancetype)responseWithBody:(NSData *)body

UnitTests/GTMHTTPServer.m

@@ -416,7 +416,20 @@ - (void)stream:(NSStream *)aStream handleEvent:(NSStreamEvent)eventCode {
             NSOutputStream *outputStream = connDict[kOutputStream];
             [outputStream scheduleInRunLoop:[NSRunLoop currentRunLoop]
                                     forMode:NSDefaultRunLoopMode];
-            [outputStream open];
+            if (response.delaySeconds) {
+              dispatch_time_t delayTime =
+                  dispatch_time(DISPATCH_TIME_NOW, (int64_t)(response.delaySeconds * NSEC_PER_SEC));
+              dispatch_after(delayTime, dispatch_get_main_queue(), ^{
+                @try {
+                  [outputStream open];
+                } @catch (NSException *e) {
+                  NSLog(@"Exception while doing a delayed response open: %@", e);
+                }  // COV_NF_LINE - radar 5851992 only reachable w/ an uncaught exception,
+                   // un-testable
+              });
+            } else {
+              [outputStream open];
+            }
           }
         }
       } @catch (NSException *e) {  // COV_NF_START
@@ -651,6 +664,8 @@ @implementation GTMHTTPResponseMessage {
   CFHTTPMessageRef _message;
 }
 
+@synthesize delaySeconds = _delaySeconds;
+
 - (instancetype)init {
   return [self initWithBody:nil contentType:nil statusCode:0];
 }

UnitTests/GTMSessionFetcherTestServer.m

@@ -505,9 +505,9 @@ - (GTMHTTPResponseMessage *)httpServer:(GTMHTTPServer *)server
 
   NSString *sleepStr = [[self class] valueForParameter:@"sleep" query:query];
   if (sleepStr) {
-    NSTimeInterval interval = [sleepStr doubleValue];
-    [NSThread sleepForTimeInterval:interval];
-    return sendResponse(408, nil, nil);  // request timeout
+    GTMHTTPResponseMessage *response = sendResponse(408, nil, nil);  // request timeout
+    response.delaySeconds = [sleepStr doubleValue];
+    return response;
   }
   if (ifMatch != nil && ![ifMatch isEqual:kEtag]) {
     // there is no match, hence this is an inconsistent PUT or DELETE