Simplify skiatest framework.

skiatest::Test class is now a simple struct.  Some
functionalty, such as counting errors or timing is now
handled elsewhere.

skiatest:Reporter is now a simpler abstract class.  The two
implementations handle test errors.

DM and pathops_unittest updated.

Review URL: https://codereview.chromium.org/830513004
diff --git a/tests/DocumentTest.cpp b/tests/DocumentTest.cpp
index 97aefcb..8bfb502 100644
--- a/tests/DocumentTest.cpp
+++ b/tests/DocumentTest.cpp
@@ -29,7 +29,7 @@
 }
 
 static void test_abortWithFile(skiatest::Reporter* reporter) {
-    SkString tmpDir = skiatest::Test::GetTmpDir();
+    SkString tmpDir = skiatest::GetTmpDir();
 
     if (tmpDir.isEmpty()) {
         return;  // TODO(edisonn): unfortunatelly this pattern is used in other
@@ -58,7 +58,7 @@
 }
 
 static void test_file(skiatest::Reporter* reporter) {
-    SkString tmpDir = skiatest::Test::GetTmpDir();
+    SkString tmpDir = skiatest::GetTmpDir();
     if (tmpDir.isEmpty()) {
         return;  // TODO(edisonn): unfortunatelly this pattern is used in other
                  // tests, but if GetTmpDir() starts returning and empty dir