Store DM failures in an array, not a single string.

This should fix the problem where a repeatedly failing test causes this assertion:
  ../../src/core/SkString.cpp:572: failed assertion "length >= 0 && length < SkToInt(kBufferSize)"

Example output:

0 GMs x 7 configs, 2 tests, 0 pictures
0 tasks left, 100 failed
Failures:
  test RTree: ../../tests/RTreeTest.cpp:77	0 != rtree.getCount()
  test RTree: ../../tests/RTreeTest.cpp:77	0 != rtree.getCount()
  test RTree: ../../tests/RTreeTest.cpp:77	0 != rtree.getCount()
  test RTree: ../../tests/RTreeTest.cpp:77	0 != rtree.getCount()
  < 95 lines elided >
  test RTree: ../../tests/RTreeTest.cpp:77	0 != rtree.getCount()
100 failures.

BUG=skia:

Review URL: https://codereview.chromium.org/741833002

2 files changed, 11 insertions, 9 deletions

diff --git a/dm/DMTestTask.cpp b/dm/DMTestTask.cpp
index ad0c3fb4f3..366087c351 100644
--- a/dm/DMTestTask.cpp
+++ b/dm/DMTestTask.cpp
@@ -35,7 +35,10 @@ void CpuTestTask::draw() {
     fTest->setReporter(&fTestReporter);
     fTest->run();
     if (!fTest->passed()) {
-        this->fail(fTestReporter.failure());
+        const SkTArray<SkString>& failures = fTestReporter.failures();
+        for (int i = 0; i < failures.count(); i++) {
+            this->fail(failures[i].c_str());
+        }
     }
 }
 
@@ -44,7 +47,10 @@ void GpuTestTask::draw(GrContextFactory* grFactory) {
     fTest->setReporter(&fTestReporter);
     fTest->run();
     if (!fTest->passed()) {
-        this->fail(fTestReporter.failure());
+        const SkTArray<SkString>& failures = fTestReporter.failures();
+        for (int i = 0; i < failures.count(); i++) {
+            this->fail(failures[i].c_str());
+        }
     }
 }
 
diff --git a/dm/DMTestTask.h b/dm/DMTestTask.h
index 9a47b35f60..2ca31e38b5 100644
--- a/dm/DMTestTask.h
+++ b/dm/DMTestTask.h
@@ -16,7 +16,7 @@ class TestReporter : public skiatest::Reporter {
 public:
   TestReporter() {}
 
-  const char* failure() const { return fFailure.c_str(); }
+  const SkTArray<SkString>& failures() const { return fFailures; }
 
 private:
   virtual bool allowExtendedTest() const SK_OVERRIDE;
@@ -27,14 +27,10 @@ private:
 
       SkString newFailure;
       failure.getFailureString(&newFailure);
-      // TODO: Better to store an array of failures?
-      if (!fFailure.isEmpty()) {
-          fFailure.append("\n\t\t");
-      }
-      fFailure.append(newFailure);
+      fFailures.push_back(newFailure);
   }
 
-  SkString fFailure;
+  SkTArray<SkString> fFailures;
 };
 
 class CpuTestTask : public CpuTask {