Bug 1901016 - Remove descriptions from text and tracing marker schemas r=profiler-reviewers,julienw

It's really not possible to add a single meaningful description to these marker
types since they can be used by various marker types. Previous descriptions
were not really descriptive or helpful for the users. They were just explaining
some implementation details which our users don't need to know.

For the implementation details, we already check if this `Description` field
is nullptr or not, and if it's falsy we don't serialize this field at all:
https://searchfox.org/mozilla-central/rev/d3fea1aa852bb3a353a0a4a875c3685da11ce39b/mozglue/baseprofiler/public/BaseProfilerMarkersPrerequisites.h#1064-1066

Differential Revision: https://phabricator.services.mozilla.com/D212956

mozglue/baseprofiler/public/BaseProfilerMarkers.h

@@ -140,7 +140,9 @@ namespace mozilla::baseprofiler::markers {
 // Most common marker type. Others are in BaseProfilerMarkerTypes.h.
 struct TextMarker : public BaseMarkerType<TextMarker> {
   static constexpr const char* Name = "Text";
-  static constexpr const char* Description = "Generic text marker";
+  // It's not possible to add a single meaningful description to this marker
+  // type since it can be used by various different markers.
+  static constexpr const char* Description = nullptr;
 
   static constexpr bool StoreName = true;
 
@@ -167,7 +169,9 @@ struct TextMarker : public BaseMarkerType<TextMarker> {
 // counterpart.
 struct Tracing : public BaseMarkerType<Tracing> {
   static constexpr const char* Name = "tracing";
-  static constexpr const char* Description = "Generic tracing marker";
+  // It's not possible to add a single meaningful description to this marker
+  // type since it can be used by various different markers.
+  static constexpr const char* Description = nullptr;
 
   static constexpr bool StoreName = true;
 

tools/profiler/tests/gtest/GeckoProfiler.cpp

@@ -3231,14 +3231,12 @@ TEST(GeckoProfiler, Markers)
             EXPECT_EQ(display[0u].asString(), "marker-chart");
             EXPECT_EQ(display[1u].asString(), "marker-table");
 
-            ASSERT_EQ(data.size(), 2u);
+            ASSERT_EQ(data.size(), 1u);
 
             ASSERT_TRUE(data[0u].isObject());
             EXPECT_EQ_JSON(data[0u]["key"], String, "name");
             EXPECT_EQ_JSON(data[0u]["label"], String, "Details");
             EXPECT_EQ_JSON(data[0u]["format"], String, "string");
-            EXPECT_EQ_JSON(data[1u]["label"], String, "Description");
-            EXPECT_EQ_JSON(data[1u]["value"], String, "Generic text marker");
 
           } else if (nameString == "NoPayloadUserData") {
             // TODO: Remove this when bug 1646714 lands.
@@ -3257,14 +3255,12 @@ TEST(GeckoProfiler, Markers)
             EXPECT_EQ(display[1u].asString(), "marker-table");
             EXPECT_EQ(display[2u].asString(), "timeline-overview");
 
-            ASSERT_EQ(data.size(), 2u);
+            ASSERT_EQ(data.size(), 1u);
 
             ASSERT_TRUE(data[0u].isObject());
             EXPECT_EQ_JSON(data[0u]["key"], String, "category");
             EXPECT_EQ_JSON(data[0u]["label"], String, "Type");
             EXPECT_EQ_JSON(data[0u]["format"], String, "string");
-            EXPECT_EQ_JSON(data[1u]["label"], String, "Description");
-            EXPECT_EQ_JSON(data[1u]["value"], String, "Generic tracing marker");
 
           } else if (nameString == "BHR-detected hang") {
             EXPECT_EQ(display.size(), 2u);