Deduplicate fuzz cases on the frontend before they are displayed.

fuzzer/go/frontend/data/stacktrace_test.go

 package data
 
 import (
         "path/filepath"
         "reflect"
         "strings"
         "testing"
 
         "go.skia.org/infra/fuzzer/go/common"
         "go.skia.org/infra/go/testutils"
@@ skipping 78 matching lines @@
 func TestParseASANSingle(t *testing.T) {
         testInput := testutils.MustReadFile("parse-asan-single.asan")
 
         trace := parseASANStackTrace(testInput)
 
         expected := StackTrace{
                 Frames: []StackTraceFrame{
                         FullStackFrame("src/codec/", "SkMasks.cpp", "convert_to_8", 54),
                         FullStackFrame("src/codec/", "SkMaskSwizzler.cpp", "swizzle_mask24_to_n32_opaque", 93),
                         FullStackFrame("src/codec/", "SkBmpMaskCodec.cpp", "SkBmpMaskCodec::decodeRows", 103),
-                        FullStackFrame("src/codec/", "SkBmpMaskCodec.cpp", "SkBmpMaskCodec::onGetPixels", 53),
-                        FullStackFrame("src/codec/", "SkCodec.cpp", "SkCodec::getPixels", 204),
+                        FullStackFrame("third_party/externals/piex/src/", "piex.cc", "piex::GetPreviewData", 59),
+                        FullStackFrame("third_party/externals/piex/src/", "piex.cc", "piex::GetPreviewData", 68),
                         FullStackFrame("fuzz/", "fuzz.cpp", "fuzz_img", 119),
                         FullStackFrame("fuzz/", "fuzz.cpp", "main", 53),
                 },
         }
 
         if !reflect.DeepEqual(expected, trace) {
                 t.Errorf("Expected %#v\nbut was %#v", expected, trace)
                 t.Errorf("Expected %s \n but was %s", expected.String(), trace.String())
         }
 }
@@ skipping 316 matching lines @@
                 t.Errorf("Top frame was wrong.  Expected: %#v, but was %#v", expected, frame)
         }
 
         if len(result.Release.StackTrace.Frames) != 1 {
                 t.Errorf("Should not have had empty release stacktrace")
         }
         if frame := result.Release.StackTrace.Frames[0]; frame.LineNumber != expected.LineNumber || frame.FunctionName != expected.FunctionName || frame.FileName != expected.FileName || frame.PackageName != expected.PackageName {
                 t.Errorf("Top frame was wrong.  Expected: %#v, but was %#v", expected, frame)
         }
 }