Add new fuzz binary.

This is designed to have short startup time, for maximum fuzzing throughput.

BUG=skia:
GOLD_TRYBOT_URL= https://gold.skia.org/search2?unt=true&query=source_type%3Dgm&master=false&issue=1589563002

Review URL: https://codereview.chromium.org/1589563002

fuzz/Fuzz.h

@@ -0,0 +1,43 @@
+/*
+ * Copyright 2016 Google Inc.
+ *
+ * Use of this source code is governed by a BSD-style license that can be
+ * found in the LICENSE file.
+ */
+
+#ifndef Fuzz_DEFINED
+#define Fuzz_DEFINED
+
+#include "SkData.h"
+#include "SkTRegistry.h"
+#include "SkTypes.h"
+#include <stdlib.h>
+
+class Fuzz : SkNoncopyable {
+public:
+    explicit Fuzz(SkData*);
+
+    uint32_t nextU();
+    float    nextF();
+
+    // These return a value in [min, max).
+    uint32_t nextURange(uint32_t min, uint32_t max);
+    float    nextFRange(float    min, float    max);
+
+private:
+    SkAutoTUnref<SkData> fBytes;
+};
+
+struct Fuzzable {
+    const char* name;
+    void (*fn)(Fuzz*);
+};
+
+#define DEF_FUZZ(name, f)                                        \
+    static void fuzz_##name(Fuzz*);                              \
+    SkTRegistry<Fuzzable> register_##name({#name, fuzz_##name}); \
+    static void fuzz_##name(Fuzz* f)
+
+#define ASSERT(cond) do { if (!(cond)) abort(); } while(false)
+
+#endif//Fuzz_DEFINED

fuzz/FuzzPaeth.cpp

@@ -0,0 +1,40 @@
+/*
+ * Copyright 2016 Google Inc.
+ *
+ * Use of this source code is governed by a BSD-style license that can be
+ * found in the LICENSE file.
+ */
+
+#include "Fuzz.h"
+
+// This really is just an example Fuzz*.cpp file.
+// It tests that two different ways of calculating the Paeth predictor function are equivalent.
+
+static uint8_t paeth_std(uint8_t a, uint8_t b, uint8_t c) {
+    int p = a+b-c;
+
+    int pa = abs(p-a),
+        pb = abs(p-b),
+        pc = abs(p-c);
+
+    if (pb < pa) { pa = pb; a = b; }
+    if (pc < pa) {          a = c; }
+    return a;
+}
+
+static uint8_t paeth_alt(uint8_t a, uint8_t b, uint8_t c) {
+    int min = SkTMin(a,b),
+        max = SkTMax(a,b);
+    int delta = (max-min)/3;
+
+    if (c <= min+delta) return max;
+    if (c >= max-delta) return min;
+    return c;
+}
+
+DEF_FUZZ(Paeth, fuzz) {
+    int a = fuzz->nextU(),
+        b = fuzz->nextU(),
+        c = fuzz->nextU();
+    ASSERT(paeth_alt(a,b,c) == paeth_std(a,b,c));
+}

fuzz/fuzz.cpp

@@ -0,0 +1,40 @@
+/*
+ * Copyright 2016 Google Inc.
+ *
+ * Use of this source code is governed by a BSD-style license that can be
+ * found in the LICENSE file.
+ */
+
+#include "Fuzz.h"
+#include "SkCommandLineFlags.h"
+
+DEFINE_string2(match, m, "", "The usual match patterns, applied to name.");
+DEFINE_string2(bytes, b, "", "Path to file containing fuzzed bytes.");
+
+int main(int argc, char** argv) {
+    SkCommandLineFlags::Parse(argc, argv);
+    SkAutoTUnref<SkData> bytes;
+    if (!FLAGS_bytes.isEmpty()) {
+        bytes.reset(SkData::NewFromFileName(FLAGS_bytes[0]));
+    }
+
+    for (auto r = SkTRegistry<Fuzzable>::Head(); r; r = r->next()) {
+        auto fuzzable = r->factory();
+        if (!SkCommandLineFlags::ShouldSkip(FLAGS_match, fuzzable.name)) {
+            SkDebugf("Running %s...\n", fuzzable.name);
+            Fuzz fuzz(bytes);
+            fuzzable.fn(&fuzz);
+        }
+    }
+    return 0;
+}
+
+
+Fuzz::Fuzz(SkData* bytes) : fBytes(SkSafeRef(bytes)) {}
+
+// These methods are all TODO(kjlubick).
+uint32_t Fuzz::nextU() { return    0; }
+float    Fuzz::nextF() { return 0.0f; }
+uint32_t Fuzz::nextURange(uint32_t min, uint32_t max) { return min; }
+float    Fuzz::nextFRange(float    min, float    max) { return min; }
+

gyp/fuzz.gyp

@@ -0,0 +1,17 @@
+# Copyright 2016 Google Inc.
+#
+# Use of this source code is governed by a BSD-style license that can be
+# found in the LICENSE file.
+
+{
+    'includes': [ 'apptype_console.gypi' ],
+    'targets': [{
+        'target_name': 'fuzz',
+        'type': 'executable',
+        'sources': [ '<!@(python find.py ../fuzz "*.cpp")' ],
+        'dependencies': [
+            'flags.gyp:flags',
+            'skia_lib.gyp:skia_lib',
+        ],
+    }],
+}

gyp/most.gyp

@@ -27,12 +27,13 @@
         'pathops_skpclip.gyp:*',
         'dm.gyp:dm',
         'visualbench.gyp:visualbench',
+        'fuzz.gyp:fuzz',
       ],
       'conditions': [
-        [ 'skia_gpu == 0', { 
-          'dependencies!': [ 
-            'visualbench.gyp:visualbench' 
-          ] 
+        [ 'skia_gpu == 0', {
+          'dependencies!': [
+            'visualbench.gyp:visualbench'
+          ]
         }],
         [ 'skia_gpu == 0 or skia_os == "android"', {
           'dependencies!': [
@@ -40,13 +41,13 @@
           ],
         }],
         ['skia_os == "android"', {
-          'dependencies': [ 
-            'android_system.gyp:SampleApp_APK', 
+          'dependencies': [
+            'android_system.gyp:SampleApp_APK',
           ],
           'conditions': [
             [ 'skia_gpu == 1', {
               'dependencies': [
-                'android_system.gyp:VisualBench_APK', 
+                'android_system.gyp:VisualBench_APK',
               ],
             }],
           ],