Deduplicate fuzz cases on the frontend before they are displayed.

fuzzer/go/deduplicator/deduplicator.go

Index: fuzzer/go/deduplicator/deduplicator.go
diff --git a/fuzzer/go/deduplicator/deduplicator.go b/fuzzer/go/deduplicator/deduplicator.go
new file mode 100644
index 0000000000000000000000000000000000000000..88ca84c6442ad7e50ecc178d3a30280f057e0fd9
--- /dev/null
+++ b/fuzzer/go/deduplicator/deduplicator.go
@@ -0,0 +1,62 @@
+package deduplicator
+
+import (
+	"fmt"
+
+	"go.skia.org/infra/fuzzer/go/frontend/data"
+	"go.skia.org/infra/go/util"
+)
+
+const _MAX_STACKTRACE_LINES = 4
+
+type Deduplicator struct {
+	seen map[string]bool
+}
+
+func New() *Deduplicator {
+	return &Deduplicator{
+		seen: make(map[string]bool),
+	}
+}
+
+func (d *Deduplicator) Clear() {
+	d.seen = make(map[string]bool)
+}
+
+func (d *Deduplicator) IsUnique(report data.FuzzReport) bool {
+	// Empty stacktraces should be manually deduplicated.
+	if report.DebugStackTrace.IsEmpty() && report.ReleaseStackTrace.IsEmpty() {
+		return true
+	}
+	// Other flags should also be looked at manually.
+	if util.In("Other", report.DebugFlags) || util.In("Other", report.ReleaseFlags) {
+		return true
+	}
+	if k := key(report); d.seen[k] {
+		return false
+	} else {
+		d.seen[k] = true
+		return true
+	}
+}
+
+func key(r data.FuzzReport) string {
+	ds := trim(r.DebugStackTrace)
+	rs := trim(r.ReleaseStackTrace)
+	return fmt.Sprintf("C:%s,F:%q,F:%q,S:%s,S:%s", r.FuzzCategory, r.DebugFlags, r.ReleaseFlags, ds.String(), rs.String())
+}
+
+// trim returns a copy of the given stacktrace, with the line numbers removed and all but the
+// first _MAX_STACKTRACE_LINES stacktraces removed.
+func trim(st data.StackTrace) data.StackTrace {
+	if frames := st.Frames; len(frames) > _MAX_STACKTRACE_LINES {
+		st.Frames = st.Frames[0:_MAX_STACKTRACE_LINES]
+	}
+	// copy the frames, so we don't accidentally change the real report.
+	st.Frames = append([]data.StackTraceFrame(nil), st.Frames...)
+	// Remove line numbers from our deduping criteria.
+	for i := range st.Frames {
+		st.Frames[i].LineNumber = 0
+	}
+	return st
+}