More efficient SkRecorder::flushMiniRecorder()

This should involve no mallocs, frees, or memcpys, and less refcounting.

BUG=skia:

Review URL: https://codereview.chromium.org/1144173002

3 files changed, 30 insertions, 6 deletions

diff --git a/src/core/SkMiniRecorder.cpp b/src/core/SkMiniRecorder.cpp
index f851e1cac0..6707e863ac 100644
--- a/src/core/SkMiniRecorder.cpp
+++ b/src/core/SkMiniRecorder.cpp
@@ -86,12 +86,13 @@ bool SkMiniRecorder::drawTextBlob(const SkTextBlob* b, SkScalar x, SkScalar y, c
 }
 #undef TRY_TO_STORE
 
+
+SkPicture* SkMiniRecorder::detachAsPicture(const SkRect& cull) {
 #define CASE(Type)               \
     case State::k##Type:         \
         fState = State::kEmpty;  \
         return SkNEW_ARGS(SkMiniPicture<Type>, (cull, reinterpret_cast<Type*>(fBuffer.get())))
 
-SkPicture* SkMiniRecorder::detachAsPicture(const SkRect& cull) {
     switch (fState) {
         case State::kEmpty: return SkNEW(SkEmptyPicture);
         CASE(DrawPath);
@@ -99,6 +100,25 @@ SkPicture* SkMiniRecorder::detachAsPicture(const SkRect& cull) {
         CASE(DrawTextBlob);
     }
     SkASSERT(false);
-    return NULL;
+    return nullptr;
+#undef CASE
 }
+
+void SkMiniRecorder::flushAndReset(SkCanvas* canvas) {
+#define CASE(Type)                                                  \
+    case State::k##Type: {                                          \
+        fState = State::kEmpty;                                     \
+        Type* op = reinterpret_cast<Type*>(fBuffer.get());          \
+        SkRecords::Draw(canvas, nullptr, nullptr, 0, nullptr)(*op); \
+        op->~Type();                                                \
+    } return
+
+    switch (fState) {
+        case State::kEmpty: return;
+        CASE(DrawPath);
+        CASE(DrawRect);
+        CASE(DrawTextBlob);
+    }
+    SkASSERT(false);
 #undef CASE
+}
diff --git a/src/core/SkMiniRecorder.h b/src/core/SkMiniRecorder.h
index d01aedacea..914eccc2e3 100644
--- a/src/core/SkMiniRecorder.h
+++ b/src/core/SkMiniRecorder.h
@@ -27,6 +27,12 @@ public:
     // Detach anything we've recorded as a picture, resetting this SkMiniRecorder.
     SkPicture* detachAsPicture(const SkRect& cull);
 
+    // Flush anything we've recorded to the canvas, resetting this SkMiniRecorder.
+    // This is logically the same as but rather more efficient than:
+    //    SkAutoTUnref<SkPicture> pic(this->detachAsPicture(SkRect::MakeEmpty()));
+    //    pic->playback(canvas);
+    void flushAndReset(SkCanvas*);
+
 private:
     enum class State { kEmpty, kDrawPath, kDrawRect, kDrawTextBlob };
 
diff --git a/src/core/SkRecorder.cpp b/src/core/SkRecorder.cpp
index 45283f8118..0989132cd2 100644
--- a/src/core/SkRecorder.cpp
+++ b/src/core/SkRecorder.cpp
@@ -136,10 +136,8 @@ char* SkRecorder::copy(const char* src) {
 void SkRecorder::flushMiniRecorder() {
     if (fMiniRecorder) {
         SkMiniRecorder* mr = fMiniRecorder;
-        fMiniRecorder = nullptr;  // Needs to happen before p->playback(this) or we loop forever.
-        // TODO: this can probably be done more efficiently by SkMiniRecorder if it matters.
-        SkAutoTUnref<SkPicture> p(mr->detachAsPicture(SkRect::MakeEmpty()));
-        p->playback(this);
+        fMiniRecorder = nullptr;  // Needs to happen before flushAndReset() or we recurse forever.
+        mr->flushAndReset(this);
     }
 }