Adding a cache + memory pool for GPU TextBlobs

src/gpu/GrTextBlobCache.cpp

+/*
+ * Copyright 2015 Google Inc.
+ *
+ * Use of this source code is governed by a BSD-style license that can be
+ * found in the LICENSE file.
+ */
+
+#include "GrTextBlobCache.h"
+
+static const int kVerticesPerGlyph = 4;
+
+GrTextBlobCache::~GrTextBlobCache() {
+    SkTDynamicHash<BitmapTextBlob, uint32_t>::Iter iter(&fCache);
+    while (!iter.done()) {
+        (&(*iter))->unref();
+        ++iter;
+    }
+}
+
+GrAtlasTextContext::BitmapTextBlob* GrTextBlobCache::createBlob(int glyphCount, int runCount,
+                                                                size_t maxVASize) {
+    // We allocate size for the BitmapTextBlob itself, plus size for the vertices array,
+    // and size for the glyphIds array.
+    size_t verticesCount = glyphCount * kVerticesPerGlyph * maxVASize;
+    size_t size = sizeof(BitmapTextBlob) +
+                  verticesCount +
+                  glyphCount * sizeof(GrGlyph::PackedID) +
+                  sizeof(BitmapTextBlob::Run) * runCount;
+
+    BitmapTextBlob* cacheBlob = SkNEW_PLACEMENT(fPool.allocate(size), BitmapTextBlob);
+
+    // setup offsets for vertices / glyphs
+    cacheBlob->fVertices = sizeof(BitmapTextBlob) + reinterpret_cast<unsigned char*>(cacheBlob);
+    cacheBlob->fGlyphIDs =
+            reinterpret_cast<GrGlyph::PackedID*>(cacheBlob->fVertices + verticesCount);
+    cacheBlob->fRuns = reinterpret_cast<BitmapTextBlob::Run*>(cacheBlob->fGlyphIDs + glyphCount);
+
+    // Initialize runs
+    for (int i = 0; i < runCount; i++) {
+        SkNEW_PLACEMENT(&cacheBlob->fRuns[i], BitmapTextBlob::Run);
+    }
+    cacheBlob->fRunCount = runCount;
+    cacheBlob->fPool = &fPool;
+    return cacheBlob;
+}