Move NV12ToYUV420 helper function out of header

... as it is only used locally in YUVConverter.cpp.

This is part of a chain of changes to refactor YUVConverter
to support YUV P010 buffers.

Bug: b/191084459
Test: cvd start --gpu_mode=gfxstream
Change-Id: I23ce3a26779c6cd3f7fca526450d90b058f39ca8
diff --git a/stream-servers/YUVConverter.cpp b/stream-servers/YUVConverter.cpp
index 22858e4..e8be035 100644
--- a/stream-servers/YUVConverter.cpp
+++ b/stream-servers/YUVConverter.cpp
@@ -42,6 +42,28 @@
     YUVInterleaveDirectionUV = 1,
 };
 
+// NV12 and YUV420 are all packed
+static void NV12ToYUV420PlanarInPlaceConvert(int nWidth,
+                                             int nHeight,
+                                             uint8_t* pFrame,
+                                             uint8_t* pQuad) {
+    std::vector<uint8_t> tmp;
+    if (pQuad == nullptr) {
+        tmp.resize(nWidth * nHeight / 4);
+        pQuad = tmp.data();
+    }
+    int nPitch = nWidth;
+    uint8_t *puv = pFrame + nPitch * nHeight, *pu = puv,
+            *pv = puv + nPitch * nHeight / 4;
+    for (int y = 0; y < nHeight / 2; y++) {
+        for (int x = 0; x < nWidth / 2; x++) {
+            pu[y * nPitch / 2 + x] = puv[y * nPitch + x * 2];
+            pQuad[y * nWidth / 2 + x] = puv[y * nPitch + x * 2 + 1];
+        }
+    }
+    memcpy(pv, pQuad, nWidth * nHeight / 4);
+}
+
 // getYUVOffsets(), given a YUV-formatted buffer that is arranged
 // according to the spec
 // https://developer.android.com/reference/android/graphics/ImageFormat.html#YUV
diff --git a/stream-servers/YUVConverter.h b/stream-servers/YUVConverter.h
index e323b54..7c8830c 100644
--- a/stream-servers/YUVConverter.h
+++ b/stream-servers/YUVConverter.h
@@ -63,28 +63,6 @@
 
     void swapTextures(uint32_t type, uint32_t* textures);
 
-    // NV12 and YUV420 are all packed
-    static void NV12ToYUV420PlanarInPlaceConvert(int nWidth,
-                                                 int nHeight,
-                                                 uint8_t* pFrame,
-                                                 uint8_t* pQuad) {
-        std::vector<uint8_t> tmp;
-        if (pQuad == nullptr) {
-            tmp.resize(nWidth * nHeight / 4);
-            pQuad = tmp.data();
-        }
-        int nPitch = nWidth;
-        uint8_t *puv = pFrame + nPitch * nHeight, *pu = puv,
-                *pv = puv + nPitch * nHeight / 4;
-        for (int y = 0; y < nHeight / 2; y++) {
-            for (int x = 0; x < nWidth / 2; x++) {
-                pu[y * nPitch / 2 + x] = puv[y * nPitch + x * 2];
-                pQuad[y * nWidth / 2 + x] = puv[y * nPitch + x * 2 + 1];
-            }
-        }
-        memcpy(pv, pQuad, nWidth * nHeight / 4);
-    }
-
     // public so other classes can call
     static void createYUVGLTex(GLenum texture_unit,
                                GLsizei width,