Make SkSHA1 and SkM5 use common SkDigestHash result type

bench/ChecksumBench.cpp

 /*

[epoger, 2013/04/15 18:21:38]

Toplevel comment: the reason for this change is: a stepping-stone for (possibly)
changing the hash algorithm used for GM image checksums, as mentioned in
https://goto.google.com/ChecksumRemainingSteps

  * Copyright 2012 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 #include "SkBenchmark.h"
 #include "SkCanvas.h"
 #include "SkChecksum.h"
 #include "SkCityHash.h"
 #include "SkMD5.h"
@@ skipping 44 matching lines @@
             case kChecksum_ChecksumType: {
                 for (int i = 0; i < N; i++) {
                     volatile uint32_t result = SkChecksum::Compute(fData, sizeof(fData));
                     sk_ignore_unused_variable(result);
                 }
             } break;
             case kMD5_ChecksumType: {
                 for (int i = 0; i < N; i++) {
                     SkMD5 md5;
                     md5.update(reinterpret_cast<uint8_t*>(fData), sizeof(fData));
-                    SkMD5::Digest digest;
+                    SkHashDigest digest;
                     md5.finish(digest);
                 }
             } break;
             case kSHA1_ChecksumType: {
                 for (int i = 0; i < N; i++) {
                     SkSHA1 sha1;
                     sha1.update(reinterpret_cast<uint8_t*>(fData), sizeof(fData));
-                    SkSHA1::Digest digest;
+                    SkHashDigest digest;
                     sha1.finish(digest);
                 }
             } break;
             case kCityHash32: {
                 for (int i = 0; i < N; i++) {
                     volatile uint32_t result = SkCityHash::Compute32(reinterpret_cast<char*>(fData), sizeof(fData));
                     sk_ignore_unused_variable(result);
                 }
             } break;
             case kCityHash64: {
@@ skipping 16 matching lines @@
 static SkBenchmark* Fact1(void* p) { return new ComputeChecksumBench(p, kMD5_ChecksumType); }
 static SkBenchmark* Fact2(void* p) { return new ComputeChecksumBench(p, kSHA1_ChecksumType); }
 static SkBenchmark* Fact3(void* p) { return new ComputeChecksumBench(p, kCityHash32); }
 static SkBenchmark* Fact4(void* p) { return new ComputeChecksumBench(p, kCityHash64); }
 
 static BenchRegistry gReg0(Fact0);
 static BenchRegistry gReg1(Fact1);
 static BenchRegistry gReg2(Fact2);
 static BenchRegistry gReg3(Fact3);
 static BenchRegistry gReg4(Fact4);