Additional metrics for disabled extensions and content verification

tools/metrics/histograms/histograms.xml

Index: tools/metrics/histograms/histograms.xml
diff --git a/tools/metrics/histograms/histograms.xml b/tools/metrics/histograms/histograms.xml
index 717ca5d79b8bf96a1be5a04a2709221968515d69..c43d883491bc35a774edd87c06c31591afe18c15 100644
--- a/tools/metrics/histograms/histograms.xml
+++ b/tools/metrics/histograms/histograms.xml
@@ -6615,6 +6615,31 @@ Therefore, the affected-histogram name has to have at least one dot in it.
   </summary>
 </histogram>
 
+<histogram name="Extensions.CorruptExtensionBecameDisabled">
+  <owner>asargent@chromium.org</owner>
+  <summary>
+    Fired each time an extension was detected to be corrupted (contents not
+    matching an expected content hash from the webstore) and was disabled.
+  </summary>
+</histogram>

[Ilya Sherman, 2014/07/24 21:55:51]

It would probably be useful for this histogram to have a built-in baseline of
how many times extensions were loaded in total (or, checked for corruption, if
that's not done at load time).  That is, assuming the main question you want to
answer is something like "What fraction of all extensions are corrupted?"

[asargent_no_longer_on_chrome, 2014/07/25 00:09:16]

This is tricky - we already have a histogram for the number of extensions that
get loaded at startup, and in this CL I've also added one that buckets disabled
extensions by the disabled reason (corrupt contents being one of those reasons).
But this one is designed to help us see the rate at which extensions are getting
disabled (does the number per day stay roughly? does it ramp up to something
high when we turn on the feature and then drop to a small number after a few
days/weeks?)

+
+<histogram name="Extensions.CorruptExtensionTotalDisables">
+  <owner>asargent@chromium.org</owner>
+  <summary>
+    Logged once at startup, this is the value of a counter that is incremented
+    anytime we disable a corrupted extension because its content didn't match an
+    expected content hash.

[Ilya Sherman, 2014/07/24 21:55:51]

So this is the total value over the lifetime of the client?  Are you concerned
at all that this has a bias that depends on the age of the client?

[asargent_no_longer_on_chrome, 2014/07/25 00:09:16]

That's an interesting thought - I don't think it will affect the kind of
analysis we want to do. This will help us answer questions like "what is the
total number of extensions that have become disabled since we turned the feature
on?". 

+  </summary>
+</histogram>
+
+<histogram name="Extensions.CorruptExtensionWouldBeDisabled">
+  <owner>asargent@chromium.org</owner>
+  <summary>
+    Simiar to Extensions.CorruptExtensionBecameDisabled, but fires when we're in
+    a bootstrapping mode and would have disabled an extension.
+  </summary>
+</histogram>
+
 <histogram name="Extensions.CrxFetchError" enum="NetErrorCodes">
   <owner>Please list the metric's owners. Add more owner tags as needed.</owner>
   <summary>Net error results from URLFetcher.</summary>
@@ -6712,6 +6737,17 @@ Therefore, the affected-histogram name has to have at least one dot in it.
   </summary>
 </histogram>
 
+<histogram name="Extensions.DisableReason" enum="ExtensionDisableReason">
+  <owner>asargent@chromium.org</owner>
+  <summary>
+    The count of disabled extensions at startup grouped by disble reason from
+    Extension::DisableReason. When an extension is disabled, it can be for one
+    or more reasons (although typically just one), so the sum of these may be
+    greater than 'Extensions.Disabled' which is a count of the number of unique
+    extensions that are disabled.
+  </summary>
+</histogram>
+
 <histogram name="Extensions.ErrorCodeFromCrxOpen">
   <owner>Please list the metric's owners. Add more owner tags as needed.</owner>
   <summary>
@@ -37934,6 +37970,22 @@ Therefore, the affected-histogram name has to have at least one dot in it.
   <int value="2" label="UNINSTALL"/>
 </enum>
 
+<enum name="ExtensionDisableReason" type="int">
+  <int value="0" label="NONE"/>

[Ilya Sherman, 2014/07/24 21:55:51]

Does "NONE" mean not disabled, or disabled for an unknown reason?

[asargent_no_longer_on_chrome, 2014/07/25 00:09:16]

This corresponds to the DISABLE_NONE enum value in Extension::DisableReason, and
means "disabled but we don't know the specific reason" (possibly because we did
not always record reasons extensions were disabled at some point in the past).

[Ilya Sherman, 2014/07/25 03:14:53]

Ok.  This is one of the rare cases where I think some tooltip text might help,
and would therefore suggest writing something like

<int value="1" label="NONE">Disabled for an unknown reason</int>

Or, even better, you could just have the label be "unknown" rather than "none"
-- though then the label doesn't match the enum value.

+  <int value="1" label="USER_ACTION"/>
+  <int value="2" label="PERMISSIONS_INCREASE"/>
+  <int value="4" label="RELOAD"/>
+  <int value="8" label="UNSUPPORTED_REQUIREMENT"/>
+  <int value="16" label="SIDELOAD_WIPEOUT"/>
+  <int value="32" label="UNKNOWN_FROM_SYNC"/>
+  <int value="64" label="DEPRECATED_PERMISSIONS_CONSENT"/>
+  <int value="128" label="DEPRECATED_KNOWN_DISABLED"/>
+  <int value="256" label="NOT_VERIFIED"/>
+  <int value="512" label="GREYLIST"/>
+  <int value="1024" label="CORRUPTED"/>
+  <int value="2048" label="REMOTE_INSTALL"/>
+</enum>
+
 <enum name="ExtensionFileWriteResult" type="int">
   <obsolete>
     Deprecated 10/2013.