[Mac] Fix weird layout issues when dragging a tab from a large screen to a small one.

BUG=http://crbug.com/27652
TEST=With two monitors of different vertical sizes connected, make a chrome window on the larger monitor, as tall as the monitor.  Drag it over to the smaller monitor and drop it.  The window should not re-layout weirdly during the drag and should continue to have a tab strip after the drop.
Review URL: http://codereview.chromium.org/385106

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@31967 0039d316-1c4b-4281-b951-d872f2087c98

3 files changed, 23 insertions, 0 deletions

diff --git a/chrome/browser/cocoa/chrome_browser_window.mm b/chrome/browser/cocoa/chrome_browser_window.mm
index 20d3c77..c4b503b 100644
--- a/chrome/browser/cocoa/chrome_browser_window.mm
+++ b/chrome/browser/cocoa/chrome_browser_window.mm
@@ -329,4 +329,18 @@ namespace {
   return shouldHideTitle_;
 }
 
+// This method is called whenever a window is moved in order to ensure it fits
+// on the screen.  We cannot always handle resizes without breaking, so we
+// prevent frame constraining in those cases.
+- (NSRect)constrainFrameRect:(NSRect)frame toScreen:(NSScreen*)screen {
+  // Do not constrain the frame rect if our delegate says no.  In this case,
+  // return the original (unconstrained) frame.
+  id delegate = [self delegate];
+  if ([delegate respondsToSelector:@selector(shouldConstrainFrameRect)] &&
+      ![delegate shouldConstrainFrameRect])
+    return frame;
+
+  return [super constrainFrameRect:frame toScreen:screen];
+}
+
 @end
diff --git a/chrome/browser/cocoa/tab_window_controller.h b/chrome/browser/cocoa/tab_window_controller.h
index 04346e5..c9c2589 100644
--- a/chrome/browser/cocoa/tab_window_controller.h
+++ b/chrome/browser/cocoa/tab_window_controller.h
@@ -49,6 +49,9 @@
 - (void)removeOverlayAfterDelay:(NSTimeInterval)delay;
 - (NSWindow*)overlayWindow;
 
+// Returns YES if it is ok to constrain the window's frame to fit the screen.
+- (BOOL)shouldConstrainFrameRect;
+
 // A collection of methods, stubbed out in this base class, that provide
 // the implementation of tab dragging based on whatever model is most
 // appropriate.
diff --git a/chrome/browser/cocoa/tab_window_controller.mm b/chrome/browser/cocoa/tab_window_controller.mm
index b627214..c8e881c 100644
--- a/chrome/browser/cocoa/tab_window_controller.mm
+++ b/chrome/browser/cocoa/tab_window_controller.mm
@@ -125,6 +125,12 @@
   return overlayWindow_;
 }
 
+- (BOOL)shouldConstrainFrameRect {
+  // If we currently have an overlay window, do not attempt to change the
+  // window's size, as our overlay window doesn't know how to resize properly.
+  return overlayWindow_ == nil;
+}
+
 - (BOOL)canReceiveFrom:(TabWindowController*)source {
   // subclass must implement
   NOTIMPLEMENTED();