Add Copy Stack button to Red Box (iOS)

Summary:
Added a button to the iOS Red Box to enable copying of the error and stack trace to the clipboard to make it easier to paste the error and stack into bug reports or other text windows. Clicking the Copy button on the bottom of the RedBox screen or pressing Cmd-Option-C keyboard shortcut in the simulator will copy the full stack trace as text to the iOS pasteboard and when in the simulator you can then hit Command-C to get the text to the Mac's pasteboard for pasting in your favorite reporting/tracking app.

No tests for this change - I don't see any tests to extend for the RCTRedBoxWindow class. No impact on APIs or core React Native functionality. I validated it by running test React Native apps with red box errors and both hitting the copy button or using the command key shortcut in the emulator to get the text of the stack to the iOS pasteboard.
![redboxcopybutton](https://cloud.githubusercontent.com/assets/7173455/15258992/7b1e849c-1903-11e6-8813-6e853db5db54.png)
Closes https://github.com/facebook/react-native/pull/7557

Differential Revision: D3311743

Pulled By: javache

fbshipit-source-id: 76d1ac8ab93f40696c6a2369dae2245194db095a

React/Modules/RCTRedBox.m

@@ -81,11 +81,22 @@
     [reloadButton setTitleColor:[UIColor whiteColor] forState:UIControlStateHighlighted];
     [reloadButton addTarget:self action:@selector(reload) forControlEvents:UIControlEventTouchUpInside];
 
-    CGFloat buttonWidth = self.bounds.size.width / 2;
+    UIButton *copyButton = [UIButton buttonWithType:UIButtonTypeCustom];
+    copyButton.autoresizingMask = UIViewAutoresizingFlexibleWidth | UIViewAutoresizingFlexibleTopMargin | UIViewAutoresizingFlexibleLeftMargin;
+    copyButton.accessibilityIdentifier = @"redbox-copy";
+    copyButton.titleLabel.font = [UIFont systemFontOfSize:14];
+    [copyButton setTitle:@"Copy (\u2325\u2318C)" forState:UIControlStateNormal];
+    [copyButton setTitleColor:[UIColor colorWithWhite:1 alpha:0.5] forState:UIControlStateNormal];
+    [copyButton setTitleColor:[UIColor whiteColor] forState:UIControlStateHighlighted];
+    [copyButton addTarget:self action:@selector(copyStack) forControlEvents:UIControlEventTouchUpInside];
+    
+    CGFloat buttonWidth = self.bounds.size.width / 3;
     dismissButton.frame = CGRectMake(0, self.bounds.size.height - buttonHeight, buttonWidth, buttonHeight);
     reloadButton.frame = CGRectMake(buttonWidth, self.bounds.size.height - buttonHeight, buttonWidth, buttonHeight);
+    copyButton.frame = CGRectMake(buttonWidth * 2, self.bounds.size.height - buttonHeight, buttonWidth, buttonHeight);
     [rootView addSubview:dismissButton];
     [rootView addSubview:reloadButton];
+    [rootView addSubview:copyButton];
   }
   return self;
 }
@@ -133,6 +144,33 @@ RCT_NOT_IMPLEMENTED(- (instancetype)initWithCoder:(NSCoder *)aDecoder)
   [_actionDelegate reloadFromRedBoxWindow:self];
 }
 
+- (void)copyStack
+{
+  NSMutableString *fullStackTrace;
+  
+  if (_lastErrorMessage != nil) {
+    fullStackTrace = [_lastErrorMessage mutableCopy];
+    [fullStackTrace appendString:@"\n\n"];
+  }
+  else {
+    fullStackTrace = [NSMutableString string];
+  }
+  
+  for (NSDictionary *stackFrame in _lastStackTrace) {
+    [fullStackTrace appendString:[NSString stringWithFormat:@"%@\n", stackFrame[@"methodName"]]];
+    if (stackFrame[@"file"]) {
+      NSString *lineInfo = [NSString stringWithFormat:@"    %@ @ %zd:%zd\n",
+                            [stackFrame[@"file"] lastPathComponent],
+                            [stackFrame[@"lineNumber"] integerValue],
+                            [stackFrame[@"column"] integerValue]];
+      [fullStackTrace appendString:lineInfo];
+    }
+  }
+  
+  UIPasteboard *pb = [UIPasteboard generalPasteboard];
+  [pb setString:fullStackTrace];
+}
+
 #pragma mark - TableView
 
 - (NSInteger)numberOfSectionsInTableView:(__unused UITableView *)tableView
@@ -240,14 +278,21 @@ RCT_NOT_IMPLEMENTED(- (instancetype)initWithCoder:(NSCoder *)aDecoder)
 
     // Dismiss red box
     [UIKeyCommand keyCommandWithInput:UIKeyInputEscape
-                        modifierFlags:0
-                               action:@selector(dismiss)],
+                       modifierFlags:0
+                              action:@selector(dismiss)],
 
     // Reload
     [UIKeyCommand keyCommandWithInput:@"r"
-                        modifierFlags:UIKeyModifierCommand
-                               action:@selector(reload)]
-  ];
+                       modifierFlags:UIKeyModifierCommand
+                              action:@selector(reload)],
+
+    // Copy = Cmd-Option C since Cmd-C in the simulator copies the pasteboard from
+    // the simulator to the desktop pasteboard.
+    [UIKeyCommand keyCommandWithInput:@"c"
+                       modifierFlags:UIKeyModifierCommand | UIKeyModifierAlternate
+                              action:@selector(copyStack)]
+
+    ];
 }
 
 - (BOOL)canBecomeFirstResponder
@@ -321,7 +366,7 @@ RCT_EXPORT_METHOD(dismiss)
   [self dismiss];
 }
 
-- (void)redBoxWindow:(RCTRedBoxWindow *)redBoxWindow openStackFrameInEditor:(NSDictionary *)stackFrame;
+- (void)redBoxWindow:(RCTRedBoxWindow *)redBoxWindow openStackFrameInEditor:(NSDictionary *)stackFrame
 {
   if (![_bridge.bundleURL.scheme hasPrefix:@"http"]) {
     RCTLogWarn(@"Cannot open stack frame in editor because you're not connected to the packager.");