Android content shell bringup.

content/public/android/java/org/chromium/content/browser/JNIHelper.java

+// Copyright (c) 2011 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+package org.chromium.content.browser;
+
+import android.graphics.Canvas;
+import android.graphics.Paint;
+import android.graphics.Rect;
+import android.graphics.Bitmap;
+import android.graphics.RectF;
+
+import java.util.HashSet;
+import java.util.Set;
+
+import org.chromium.base.CalledByNative;
+
+class JNIHelper {
+    // Holder for content backing store bitmaps of all ChromeViews.  Note that
+    // when in software mode, this will be one of the main consumers of RAM in
+    // the Java code.  This data structure exists solely to prevent garbage
+    // collection and expose the allocations to the DDMS tool.  The backing
+    // stores are actually used in C++ with weak global references.
+    private static final Set<Bitmap> mBitmapHolder = new HashSet<Bitmap>();
+
+    @CalledByNative
+    private static Bitmap createJavaBitmap(int w, int h, boolean keep) {
+        Bitmap newBitmap =
+            Bitmap.createBitmap(w, h, Bitmap.Config.ARGB_8888);
+
+        if (keep) {
+          mBitmapHolder.add(newBitmap);
+        }
+
+        return newBitmap;
+    }
+
+    @CalledByNative
+    private static void deleteJavaBitmap(Bitmap b) {
+      mBitmapHolder.remove(b);
+      b.recycle();
+    }
+
+    // Statics used transiently in paintJavaBitmapToJavaBitmap, but retained to reduce
+    // heap churn on each call to that method.
+    static private Rect sSourceRect;
+    static private RectF sDestRect;
+    static private Canvas sCanvas;
+    static private Bitmap sNullBitmap;
+    static private Paint sPaint;
+
+    @CalledByNative
+    public static void paintJavaBitmapToJavaBitmap(
+            Bitmap sourceBitmap,
+            int sourceX, int sourceY, int sourceBottom, int sourceRight,
+            Bitmap destBitmap,
+            float destX, float destY, float destBottom, float destRight) {
+        if (sCanvas == null) {
+            sSourceRect = new Rect();
+            sDestRect = new RectF();
+            sCanvas = new Canvas();
+            sNullBitmap = Bitmap.createBitmap(1, 1, Bitmap.Config.ALPHA_8);
+            sPaint = new Paint(Paint.FILTER_BITMAP_FLAG);
+        }
+        sSourceRect.set(sourceX, sourceY, sourceRight, sourceBottom);
+        sDestRect.set(destX, destY, destRight, destBottom);
+        sCanvas.setBitmap(destBitmap);
+        sCanvas.drawBitmap(sourceBitmap, sSourceRect, sDestRect, sPaint);
+        sCanvas.setBitmap(sNullBitmap);  // To release |destBitmap| reference.
+    }
+}