Port GrGLCaps over to use SkTHash.

tests/HashTest.cpp

 #include "SkChecksum.h"
 #include "SkString.h"
 #include "SkTHash.h"
 #include "Test.h"
 
 namespace { uint32_t hash_int(const int& k) { return SkChecksum::Mix(k); } }
 
 static void set_negative_key(int key, double* d) { *d = -key; }
 
 DEF_TEST(HashMap, r) {
@@ skipping 21 matching lines @@
     for (int i = 0; i < N; i++) {
         double* found = map.find(i);;
         REPORTER_ASSERT(r, found);
         REPORTER_ASSERT(r, *found == i*2.0);
     }
     for (int i = N; i < 2*N; i++) {
         REPORTER_ASSERT(r, !map.find(i));
     }
 
     REPORTER_ASSERT(r, map.count() == N);
+
+    map.reset();
+    REPORTER_ASSERT(r, map.count() == 0);
 }
 
 namespace { uint32_t hash_string(const SkString& s) { return SkToInt(s.size()); } }
 
 DEF_TEST(HashSet, r) {
     SkTHashSet<SkString, hash_string> set;
 
     set.add(SkString("Hello"));
     set.add(SkString("World"));
 
     REPORTER_ASSERT(r, set.count() == 2);
 
     REPORTER_ASSERT(r, set.contains(SkString("Hello")));
     REPORTER_ASSERT(r, set.contains(SkString("World")));
     REPORTER_ASSERT(r, !set.contains(SkString("Goodbye")));
+
+    set.reset();
+    REPORTER_ASSERT(r, set.count() == 0);
 }
 
 namespace {
 
 class CopyCounter {
 public:
     CopyCounter() : fID(0), fCounter(NULL) {}
 
     CopyCounter(uint32_t id, uint32_t* counter) : fID(id), fCounter(counter) {}
 
@@ skipping 44 matching lines @@
     set.add(copyCounter2);
     REPORTER_ASSERT(r, globalCounter == 3);
     REPORTER_ASSERT(r, set.contains(copyCounter1));
     REPORTER_ASSERT(r, set.contains(copyCounter2));
     REPORTER_ASSERT(r, globalCounter == 3);
     set.add(copyCounter1);
     set.add(copyCounter2);
     // We allow copies for same-value adds for now.
     REPORTER_ASSERT(r, globalCounter == 5);
 }