Make UMA_HISTOGRAM_ENUMERATION work with scoped enums.

media/blink/resource_multibuffer_data_provider.cc

Index: media/blink/resource_multibuffer_data_provider.cc
diff --git a/media/blink/resource_multibuffer_data_provider.cc b/media/blink/resource_multibuffer_data_provider.cc
index f1f80f07823f60f9f15875d87437c18f44b13d8c..e812a97e53035434f2bb0194794187a550e8c97c 100644
--- a/media/blink/resource_multibuffer_data_provider.cc
+++ b/media/blink/resource_multibuffer_data_provider.cc
@@ -263,8 +263,8 @@ void ResourceMultiBufferDataProvider::didReceiveResponse(
   while (reasons) {
     DCHECK_LT(shift, max_enum);  // Sanity check.
     if (reasons & 0x1) {
-      UMA_HISTOGRAM_ENUMERATION("Media.UncacheableReason", shift,
-                                max_enum);  // PRESUBMIT_IGNORE_UMA_MAX
+      UMA_HISTOGRAM_EXACT_LINEAR("Media.UncacheableReason", shift,

[rkaplow, 2017/03/29 18:02:51]

not sure why this can't be an enum either. Add a TODO to fix?

[dcheng, 2017/03/29 18:24:41]

I think it's because the enum itself is a bitmask style enum, so we'd have to
define two separate enums to make this work out nicely. Do you still want a
TODO?

[rkaplow, 2017/03/29 23:21:17]

Well, the team can evaluate if they want to change. LINEAR is intended for
capturing numeric data with linear sized buckets. It may be worth to have the
bitmask map to an underlying enum and they can use that.

If we want to keep it like this I'd at least have a comment explaining why we're
faking an enum with a linear macro

[dcheng, 2017/03/30 00:41:59]

Done.

+                                 max_enum);  // PRESUBMIT_IGNORE_UMA_MAX
     }
 
     reasons >>= 1;