diff --git a/brightray/browser/mac/bry_inspectable_web_contents_view.h b/brightray/browser/mac/bry_inspectable_web_contents_view.h
index 8cf7540b60f9..ea6e3f9a8115 100644
--- a/brightray/browser/mac/bry_inspectable_web_contents_view.h
+++ b/brightray/browser/mac/bry_inspectable_web_contents_view.h
@@ -5,6 +5,8 @@
 #include "base/mac/scoped_nsobject.h"
 #include "ui/base/cocoa/base_view.h"
 
+@class CAShapeLayer;
+
 namespace brightray {
 class InspectableWebContentsViewMac;
 }
@@ -19,6 +21,9 @@ using brightray::InspectableWebContentsViewMac;
   BOOL devtools_visible_;
   BOOL devtools_docked_;
 
+  // Weak reference to the mask of the hosted layer.
+  CAShapeLayer* layerMask_;
+
   DevToolsContentsResizingStrategy strategy_;
 }
 
diff --git a/brightray/browser/mac/bry_inspectable_web_contents_view.mm b/brightray/browser/mac/bry_inspectable_web_contents_view.mm
index 7fb76539fc07..a7f4134b4fae 100644
--- a/brightray/browser/mac/bry_inspectable_web_contents_view.mm
+++ b/brightray/browser/mac/bry_inspectable_web_contents_view.mm
@@ -1,14 +1,24 @@
 #include "browser/mac/bry_inspectable_web_contents_view.h"
 
+#import <QuartzCore/QuartzCore.h>
+
 #include "browser/inspectable_web_contents_impl.h"
 #include "browser/inspectable_web_contents_view_mac.h"
 
 #include "content/public/browser/render_widget_host_view.h"
-#import "ui/base/cocoa/underlay_opengl_hosting_window.h"
+#include "ui/base/cocoa/animation_utils.h"
+#include "ui/base/cocoa/underlay_opengl_hosting_window.h"
 #include "ui/gfx/mac/scoped_ns_disable_screen_updates.h"
 
 using namespace brightray;
 
+namespace {
+
+// The radius of the rounded corners.
+const CGFloat kRoundedCornerRadius = 4;
+
+}  // namespace
+
 @implementation BRYInspectableWebContentsView
 
 - (instancetype)initWithInspectableWebContentsViewMac:(InspectableWebContentsViewMac*)view {
@@ -26,8 +36,14 @@ using namespace brightray;
   [self addSubview:contentsView];
 
   // See https://code.google.com/p/chromium/issues/detail?id=348490.
+  ScopedCAActionDisabler disabler;
+  base::scoped_nsobject<CALayer> layer([[CALayer alloc] init]);
+  [self setLayer:layer];
   [self setWantsLayer:YES];
 
+  // See https://code.google.com/p/chromium/issues/detail?id=396264.
+  [self updateLayerMask];
+
   return self;
 }
 
@@ -35,6 +51,12 @@ using namespace brightray;
   [self adjustSubviews];
 }
 
+// Every time the frame's size changes, the layer mask needs to be updated.
+- (void)setFrameSize:(NSSize)newSize {
+  [super setFrameSize:newSize];
+  [self updateLayerMask];
+}
+
 - (IBAction)showDevTools:(id)sender {
   inspectableWebContentsView_->inspectable_web_contents()->ShowDevTools();
 }
@@ -152,6 +174,58 @@ using namespace brightray;
   [contentsView setFrame:[self flipRectToNSRect:new_contents_bounds]];
 }
 
+// Creates a path whose bottom two corners are rounded.
+// Caller takes ownership of the path.
+- (CGPathRef)createRoundedBottomCornersPath:(NSSize)size {
+  CGMutablePathRef path = CGPathCreateMutable();
+  CGFloat width = size.width;
+  CGFloat height = size.height;
+  CGFloat cornerRadius = kRoundedCornerRadius;
+
+  // Top left corner.
+  CGPathMoveToPoint(path, NULL, 0, height);
+
+  // Top right corner.
+  CGPathAddLineToPoint(path, NULL, width, height);
+
+  // Bottom right corner.
+  CGPathAddArc(path,
+               NULL,
+               width - cornerRadius,
+               cornerRadius,
+               cornerRadius,
+               0,
+               -M_PI_2,
+               true);
+
+  // Bottom left corner.
+  CGPathAddArc(path,
+               NULL,
+               cornerRadius,
+               cornerRadius,
+               cornerRadius,
+               -M_PI_2,
+               -M_PI,
+               true);
+
+  // Draw line back to top-left corner.
+  CGPathAddLineToPoint(path, NULL, 0, height);
+  CGPathCloseSubpath(path);
+  return path;
+}
+
+// Updates the path of the layer mask to have make window have round corner.
+- (void)updateLayerMask {
+  if (![self layer].mask) {
+    layerMask_ = [CAShapeLayer layer];
+    [self layer].mask = layerMask_;
+  }
+
+  CGPathRef path = [self createRoundedBottomCornersPath:self.bounds.size];
+  layerMask_.path = path;
+  CGPathRelease(path);
+}
+
 #pragma mark - NSWindowDelegate
 
 - (void)windowWillClose:(NSNotification*)notification {