[tracing] Allow enabling heap profiling from chrome://flags

chrome/browser/flag_descriptions.h

Index: chrome/browser/flag_descriptions.h
diff --git a/chrome/browser/flag_descriptions.h b/chrome/browser/flag_descriptions.h
index ba0e2b950184bfeabc7ed8e54a2c30fd32a45f60..3bfd92b559ff4445cceaa19ee8cfd9eba8cf26c0 100644
--- a/chrome/browser/flag_descriptions.h
+++ b/chrome/browser/flag_descriptions.h
@@ -3320,6 +3320,12 @@ extern const char kAutoplayPolicyNoUserGestureRequired[];
 // Description of the autoplay policy that requires a user gesture.
 extern const char kAutoplayPolicyUserGestureRequired[];
 
+extern const char kEnableHeapProfilingName[];

[Wez, 2017/04/28 17:17:12]

nit: Can we have a brief comment on this block to explain these?

[DmitrySkiba, 2017/04/28 19:39:13]

Do you really want to add comments like "Name of the enable heap profiling flag"
and "Description of the enable heap profiling flag"? Note that most strings
above were moved from xml, where they were mandatory (I think).

I think that's enough that this file (and the namespace) is named
flag_descriptions.

[Wez, 2017/04/29 01:15:10]

The problem is that at-a-glance these look odd - the first two are actually the
name & description for the --enable-heap-profiling flag, while the rest are the
mode flags.

So a pair of comments like:

// Name & description for the heap profiling flag.
...

// Descriptions of the different heap profiling modes.
...

would help clarify why e.g. the first two end in Name and Desription and the
rest don't.

+extern const char kEnableHeapProfilingDescription[];
+extern const char kEnableHeapProfilingModePseudo[];

[Wez, 2017/04/28 17:17:12]

See comment re kEnable... naming for the mode strings. These should still end in
Description, though.

[DmitrySkiba, 2017/04/28 19:39:13]

I'm not sure, consider the full name:
flag_descriptions::kEnableHeapProfilingModeNative, so it's a description for
kEnableHeapProfilingModeNative flag.

flag_descriptions::kEnableHeapProfilingModeNativeDescription looks worse IMO.

[Wez, 2017/04/29 01:15:10]

Agreed; I was mis-reading the convention based on kEnable...Description[] above.

+extern const char kEnableHeapProfilingModeNative[];
+extern const char kEnableHeapProfilingTaskProfiler[];
+
 }  // namespace flag_descriptions
 
 #endif  // CHROME_BROWSER_FLAG_DESCRIPTIONS_H_