Add KeepaliveImpulse to extension process manager.

Impulses are an efficient way to handle certain types
of activity from extensions. E.g. the work in progress
to keep NaCl plugins in background pages alive. An
Increment / Decrement approach would require extensive
and fragile instrumentation of all APIs. Impulses
can be sent upon any api activity and act as an
implicit increment with a timed out decrement.

See design doc:
https://docs.google.com/a/chromium.org/document/d/1mI0lS1rfAf-BAGLmWAEcWy37Xq9dOvgfMx8OqeUMXts/edit#

BUG=298339

Review URL: https://codereview.chromium.org/60613004

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@238261 0039d316-1c4b-4281-b951-d872f2087c98

1 files changed, 3 insertions, 3 deletions

diff --git a/extensions/common/switches.cc b/extensions/common/switches.cc
index 82222c4..5d50344 100644
--- a/extensions/common/switches.cc
+++ b/extensions/common/switches.cc
@@ -34,12 +34,12 @@ const char kEnableExperimentalExtensionApis[] =
 // them in the chrome:extensions page.
 const char kErrorConsole[] = "error-console";
 
-// The time in seconds that an extension event page can be idle before it
+// The time in milliseconds that an extension event page can be idle before it
 // is shut down.
 const char kEventPageIdleTime[]             = "event-page-idle-time";
 
-// The time in seconds that an extension event page has between being notified
-// of its impending unload and that unload happening.
+// The time in milliseconds that an extension event page has between being
+// notified of its impending unload and that unload happening.
 const char kEventPageSuspendingTime[]       = "event-page-unloading-time";
 
 // Enables extensions running scripts on chrome:// URLs.