--- a/gfx/thebes/gfxPlatformMac.cpp
+++ b/gfx/thebes/gfxPlatformMac.cpp
@@ -76,28 +76,16 @@ DisableFontActivation()
 
 gfxPlatformMac::gfxPlatformMac()
 {
     DisableFontActivation();
     mFontAntiAliasingThreshold = ReadAntiAliasingThreshold();
 
     InitBackendPrefs(GetBackendPrefs());
 
-    // XXX: Bug 1036682 - we run out of fds on Mac when using tiled layers because
-    // with 256x256 tiles we can easily hit the soft limit of 800 when using double
-    // buffered tiles in e10s, so let's bump the soft limit to the hard limit for the OS
-    // up to a new cap of OPEN_MAX.
-    struct rlimit limits;
-    if (getrlimit(RLIMIT_NOFILE, &limits) == 0) {
-        limits.rlim_cur = std::min(rlim_t(OPEN_MAX), limits.rlim_max);
-        if (setrlimit(RLIMIT_NOFILE, &limits) != 0) {
-            NS_WARNING("Unable to bump RLIMIT_NOFILE to the maximum number on this OS");
-        }
-    }
-
     MacIOSurfaceLib::LoadLibrary();
 }
 
 gfxPlatformMac::~gfxPlatformMac()
 {
     gfxCoreTextShaper::Shutdown();
 }
 

--- a/toolkit/xre/nsAppRunner.cpp
+++ b/toolkit/xre/nsAppRunner.cpp
@@ -148,19 +148,22 @@
 #include "mozilla/Omnijar.h"
 #include "mozilla/StartupTimeline.h"
 #include "mozilla/LateWriteChecks.h"
 
 #include <stdlib.h>
 #include <locale.h>
 
 #ifdef XP_UNIX
+#include <errno.h>
+#include <pwd.h>
+#include <string.h>
+#include <sys/resource.h>
 #include <sys/stat.h>
 #include <unistd.h>
-#include <pwd.h>
 #endif
 
 #ifdef XP_WIN
 #include <process.h>
 #include <shlobj.h>
 #include "mozilla/WinDllServices.h"
 #include "nsThreadUtils.h"
 #include <comdef.h>
@@ -3079,16 +3082,45 @@ CheckForUserMismatch()
 #else // !XP_UNIX || ANDROID
 static bool
 CheckForUserMismatch()
 {
   return false;
 }
 #endif
 
+static void
+IncreaseDescriptorLimits()
+{
+#ifdef XP_UNIX
+  // Increase the fd limit to accomodate IPC resources like shared memory.
+  static const rlim_t kFDs = 4096;
+  struct rlimit rlim;
+
+  if (getrlimit(RLIMIT_NOFILE, &rlim) != 0) {
+    Output(false, "getrlimit: %s\n", strerror(errno));
+    return;
+  }
+  // Don't decrease the limit if it's already high enough, but don't
+  // try to go over the hard limit.  (RLIM_INFINITY isn't required to
+  // be the numerically largest rlim_t, so don't assume that.)
+  if (rlim.rlim_cur != RLIM_INFINITY && rlim.rlim_cur < kFDs &&
+      rlim.rlim_cur < rlim.rlim_max) {
+    if (rlim.rlim_max != RLIM_INFINITY && rlim.rlim_max < kFDs) {
+      rlim.rlim_cur = rlim.rlim_max;
+    } else {
+      rlim.rlim_cur = kFDs;
+    }
+    if (setrlimit(RLIMIT_NOFILE, &rlim) != 0) {
+      Output(false, "setrlimit: %s\n", strerror(errno));
+    }
+  }
+#endif
+}
+
 /*
  * XRE_mainInit - Initial setup and command line parameter processing.
  * Main() will exit early if either return value != 0 or if aExitFlag is
  * true.
  */
 int
 XREMain::XRE_mainInit(bool* aExitFlag)
 {
@@ -3149,16 +3181,18 @@ XREMain::XRE_mainInit(bool* aExitFlag)
   nsresult rv;
   ArgResult ar;
 
 #ifdef DEBUG
   if (PR_GetEnv("XRE_MAIN_BREAK"))
     NS_BREAK();
 #endif
 
+  IncreaseDescriptorLimits();
+
 #ifdef USE_GLX_TEST
   // bug 639842 - it's very important to fire this process BEFORE we set up
   // error handling. indeed, this process is expected to be crashy, and we
   // don't want the user to see its crashes. That's the whole reason for
   // doing this in a separate process.
   //
   // This call will cause a fork and the fork will terminate itself separately
   // from the usual shutdown sequence

--- a/toolkit/xre/nsSigHandlers.cpp
+++ b/toolkit/xre/nsSigHandlers.cpp
@@ -282,40 +282,16 @@ void InstallSignalHandlers(const char *a
     m *= (1024*1024);
     struct rlimit r;
     r.rlim_cur = m;
     r.rlim_max = m;
     setrlimit(RLIMIT_AS, &r);
   }
 #endif
 
-#if defined(SOLARIS)
-#define NOFILES 512
-
-    // Boost Solaris file descriptors
-    {
-	struct rlimit rl;
-
-	if (getrlimit(RLIMIT_NOFILE, &rl) == 0)
-
-	    if (rl.rlim_cur < NOFILES) {
-		rl.rlim_cur = NOFILES;
-
-		if (setrlimit(RLIMIT_NOFILE, &rl) < 0) {
-		    perror("setrlimit(RLIMIT_NOFILE)");
-		    fprintf(stderr, "Cannot exceed hard limit for open files");
-		}
-#if defined(DEBUG)
-	    	if (getrlimit(RLIMIT_NOFILE, &rl) == 0)
-		    printf("File descriptors set to %d\n", rl.rlim_cur);
-#endif //DEBUG
-	    }
-    }
-#endif //SOLARIS
-
 #if defined(MOZ_WIDGET_GTK) && (GLIB_MAJOR_VERSION > 2 || (GLIB_MAJOR_VERSION == 2 && GLIB_MINOR_VERSION >= 6))
   const char *assertString = PR_GetEnv("XPCOM_DEBUG_BREAK");
   if (assertString &&
       (!strcmp(assertString, "suspend") ||
        !strcmp(assertString, "stack") ||
        !strcmp(assertString, "abort") ||
        !strcmp(assertString, "trap") ||
        !strcmp(assertString, "break"))) {