Introduce SampleCount to ProfilesSink (#11225)

<!--Ex. Fixing a bug - Describe the bug and how this fixes the issue.
Ex. Adding a feature - Explain what this achieves.-->
#### Description

This is an extraction from
#11131.

cc @mx-psi

.chloggen/consumertest-profiles-samplecount.yaml

@@ -0,0 +1,20 @@
+# Use this changelog template to create an entry for release notes.
+
+# One of 'breaking', 'deprecation', 'new_component', 'enhancement', 'bug_fix'
+change_type: 'enhancement'
+
+# The name of the component, or a single word describing the area of concern, (e.g. otlpreceiver)
+component: consumertest
+
+# A brief description of the change.  Surround your text with quotes ("") if it needs to start with a backtick (`).
+note: Introduce SampleCount method in ProfilesSink struct.
+
+# One or more tracking issues or pull requests related to the change
+issues: [11225]
+
+# Optional: The change log or logs in which this entry should be included.
+# e.g. '[user]' or '[user, api]'
+# Include 'user' if the change is relevant to end users.
+# Include 'api' if there is a change to a library API.
+# Default: '[user]'
+change_logs: [api]

consumer/consumertest/sink.go

@@ -163,8 +163,9 @@ func (sle *LogsSink) Reset() {
 // stores all profiles and allows querying them for testing.
 type ProfilesSink struct {
 	nonMutatingConsumer
-	mu       sync.Mutex
-	profiles []pprofile.Profiles
+	mu          sync.Mutex
+	profiles    []pprofile.Profiles
+	sampleCount int
 }
 
 var _ consumerprofiles.Profiles = (*ProfilesSink)(nil)
@@ -175,6 +176,7 @@ func (ste *ProfilesSink) ConsumeProfiles(_ context.Context, td pprofile.Profiles
 	defer ste.mu.Unlock()
 
 	ste.profiles = append(ste.profiles, td)
+	ste.sampleCount += td.SampleCount()
 
 	return nil
 }
@@ -189,10 +191,18 @@ func (ste *ProfilesSink) AllProfiles() []pprofile.Profiles {
 	return copyProfiles
 }
 
+// ProfileRecordCount returns the number of profiles stored by this sink since last Reset.
+func (ste *ProfilesSink) SampleCount() int {
+	ste.mu.Lock()
+	defer ste.mu.Unlock()
+	return ste.sampleCount
+}
+
 // Reset deletes any stored data.
 func (ste *ProfilesSink) Reset() {
 	ste.mu.Lock()
 	defer ste.mu.Unlock()
 
 	ste.profiles = nil
+	ste.sampleCount = 0
 }

consumer/consumertest/sink_test.go

@@ -71,6 +71,8 @@ func TestProfilesSink(t *testing.T) {
 		want = append(want, td)
 	}
 	assert.Equal(t, want, sink.AllProfiles())
+	assert.Equal(t, len(want), sink.SampleCount())
 	sink.Reset()
 	assert.Empty(t, sink.AllProfiles())
+	assert.Empty(t, sink.SampleCount())
 }