Add Histogram Macros to Skia

Adds a set of histogram macros to Skia, modeled after Chrome's
UMA_HISTOGRAM_* macros. These allow logging of high frequency events,
and are useful to analyze real world usage of certain features.

By default, these macros are no-ops. Users can provide a custom
header file which defines these macros if they wish to collect
histogram data. Chrome will provide such a header.

I've currently only added two macros:
- SK_HISTOGRAM_BOOLEAN - logs a true/false type relationship (whether
we are tiling a texture or not on each draw).
- SK_HISTOGRAM_ENUMERATION - logs a set of potential values (which of
a number of choices were selected for the texture upload path).

We could add more unused macros at the moment, but it seems easier to
add these as needed, WDYT?

BUG=skia:
GOLD_TRYBOT_URL= https://gold.skia.org/search2?unt=true&query=source_type%3Dgm&master=false&issue=1652053004

Review URL: https://codereview.chromium.org/1652053004

1 files changed, 8 insertions, 0 deletions

diff --git a/include/config/SkUserConfig.h b/include/config/SkUserConfig.h
index a0f6258281..a3e40ec5db 100644
--- a/include/config/SkUserConfig.h
+++ b/include/config/SkUserConfig.h
@@ -146,4 +146,12 @@
  */
 //#define SK_PDF_USE_PATHOPS_CLIPPING
 
+/* Skia makes use of histogram logging macros to trace the frequency of
+ * events. By default, Skia provides no-op versions of these macros.
+ * Skia consumers can provide their own definitions of these macros to
+ * integrate with their histogram collection backend.
+ */
+//#define SK_HISTOGRAM_BOOLEAN(name, value)
+//#define SK_HISTOGRAM_ENUMERATION(name, value, boundary_value)
+
 #endif