[SessionStorageS13N] Enabling mojo SessionStorage by default

Bug: 716490
Change-Id: I08c9bc35d1e9f8f86adc6c88fb7ab8069bcf7e8f
Reviewed-on: https://chromium-review.googlesource.com/1072918Reviewed-by: Marijn Kruisselbrink <mek@chromium.org>
Reviewed-by: John Abd-El-Malek <jam@chromium.org>
Commit-Queue: Daniel Murphy <dmurph@chromium.org>
Cr-Commit-Position: refs/heads/master@{#563169}

content/public/common/content_features.cc

@@ -224,7 +224,7 @@ const base::Feature kModuleScriptsImportMetaUrl{
 
 // Mojo-based Session Storage.
 const base::Feature kMojoSessionStorage{"MojoSessionStorage",
-                                        base::FEATURE_DISABLED_BY_DEFAULT};
+                                        base::FEATURE_ENABLED_BY_DEFAULT};
 
 // Enables/disables the video capture service.
 const base::Feature kMojoVideoCapture {