Zero-sized windows are bad.

ui/base/cocoa/underlay_opengl_hosting_window.mm

Index: ui/base/cocoa/underlay_opengl_hosting_window.mm
diff --git a/ui/base/cocoa/underlay_opengl_hosting_window.mm b/ui/base/cocoa/underlay_opengl_hosting_window.mm
index 6ed0624a6a3652537d10205c4d4b5240d1c53604..b82decd98d7e9b238c680e1317e24c51a08b038e 100644
--- a/ui/base/cocoa/underlay_opengl_hosting_window.mm
+++ b/ui/base/cocoa/underlay_opengl_hosting_window.mm
@@ -87,6 +87,20 @@ void RootDidAddSubview(id self, SEL _cmd, NSView* subview) {
                 styleMask:(NSUInteger)windowStyle
                   backing:(NSBackingStoreType)bufferingType
                     defer:(BOOL)deferCreation {
+  // It is invalid to create windows with zero width or height. It screws things
+  // up royally:
+  // - It causes console spew: <http://crbug.com/78973>
+  // - It breaks Expose: <http://sourceforge.net/projects/heat-meteo/forums/forum/268087/topic/4582610>
+  //
+  // This is a banned practice
+  // <http://www.chromium.org/developers/coding-style/cocoa-dos-and-donts>. Do
+  // not do this. Use kWindowSizeDeterminedLater in
+  // ui/base/cocoa/window_size_constants.h instead.
+  //
+  // (This is checked here because UnderlayOpenGLHostingWindow is the base of
+  // most Chromium windows, not because this is related to its functionality.)
+  DCHECK(contentRect.size.width > 0 &&
+         contentRect.size.height > 0);
   if ((self = [super initWithContentRect:contentRect
                                styleMask:windowStyle
                                  backing:bufferingType