diff --git a/dom/plugins/ipc/PluginProcessChild.cpp b/dom/plugins/ipc/PluginProcessChild.cpp
index ad2df0248458..3dc2610cd6ea 100644
--- a/dom/plugins/ipc/PluginProcessChild.cpp
+++ b/dom/plugins/ipc/PluginProcessChild.cpp
@@ -13,6 +13,13 @@
 #include "base/string_util.h"
 #include "chrome/common/chrome_switches.h"
 
+#if defined(XP_MACOSX)
+#include "nsCocoaFeatures.h"
+// An undocumented CoreGraphics framework method, present in the same form
+// since at least OS X 10.5.
+extern "C" CGError CGSSetDebugOptions(int options);
+#endif
+
 #ifdef XP_WIN
 #include <objbase.h>
 bool ShouldProtectPluginCurrentDirectory(char16ptr_t pluginFilePath);
@@ -119,9 +126,21 @@ PluginProcessChild::Init()
       return false;
     }
 
-    return mPlugin.InitForChrome(pluginFilename, ParentHandle(),
-                                 IOThreadChild::message_loop(),
-                                 IOThreadChild::channel());
+    bool retval = mPlugin.InitForChrome(pluginFilename, ParentHandle(),
+                                        IOThreadChild::message_loop(),
+                                        IOThreadChild::channel());
+#if defined(XP_MACOSX)
+    if (nsCocoaFeatures::OnYosemiteOrLater()) {
+      // Explicitly turn off CGEvent logging.  This works around bug 1092855.
+      // If there are already CGEvents in the log, turning off logging also
+      // causes those events to be written to disk.  But at this point no
+      // CGEvents have yet been processed.  CGEvents are events (usually
+      // input events) pulled from the WindowServer.  An option of 0x80000008
+      // turns on CGEvent logging.
+      CGSSetDebugOptions(0x80000007);
+    }
+#endif
+    return retval;
 }
 
 void
diff --git a/widget/cocoa/nsAppShell.mm b/widget/cocoa/nsAppShell.mm
index 5f096ad5093f..2d14edea2c7b 100644
--- a/widget/cocoa/nsAppShell.mm
+++ b/widget/cocoa/nsAppShell.mm
@@ -221,6 +221,11 @@ RemoveScreenWakeLockListener()
     sWakeLockListener = nullptr;
   }
 }
+
+// An undocumented CoreGraphics framework method, present in the same form
+// since at least OS X 10.5.
+extern "C" CGError CGSSetDebugOptions(int options);
+
 // Init
 //
 // Loads the nib (see bug 316076c21) and sets up the CFRunLoopSource used to
@@ -304,6 +309,16 @@ nsAppShell::Init()
     gAppShellMethodsSwizzled = true;
   }
 
+  if (nsCocoaFeatures::OnYosemiteOrLater()) {
+    // Explicitly turn off CGEvent logging.  This works around bug 1092855.
+    // If there are already CGEvents in the log, turning off logging also
+    // causes those events to be written to disk.  But at this point no
+    // CGEvents have yet been processed.  CGEvents are events (usually
+    // input events) pulled from the WindowServer.  An option of 0x80000008
+    // turns on CGEvent logging.
+    CGSSetDebugOptions(0x80000007);
+  }
+
   [localPool release];
 
   return rv;