Default initialize CanvasPaintT<T> bitmaps to 0, 0, 0, 0.

PlatformCanvas objects are constructed uninitialized.  (Since change http://src.chromium.org/viewvc/chrome?view=rev&revision=127196).  This change had propagated uninitialized semantics to CanvasPaint<..>, and CanvasPaintSkia, which introduced the regressions mentioned in the bug below.

This change re-introduces the initilized memory behaviour, but at the CanvasPaint<T> level.  This preserves the performance boost from rev 127196, and prevents regressions in displayed UI elements.

Change also removes a now-unnecessary clear in browser_action_button.mm introduced by http://codereview.chromium.org/9839012.

BUG=118755
TEST=None
Review URL: https://chromiumcodereview.appspot.com/9837043

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@128574 0039d316-1c4b-4281-b951-d872f2087c98

5 files changed, 13 insertions, 0 deletions

diff --git a/skia/ext/canvas_paint_gtk.h b/skia/ext/canvas_paint_gtk.h
index ade49af..8060140 100644
--- a/skia/ext/canvas_paint_gtk.h
+++ b/skia/ext/canvas_paint_gtk.h
@@ -18,6 +18,7 @@ namespace skia {
 // A class designed to translate skia painting into a region in a GdkWindow.
 // On construction, it will set up a context for painting into, and on
 // destruction, it will commit it to the GdkWindow.
+// Note: The created context is always inialized to (0, 0, 0, 0).
 template <class T>
 class CanvasPaintT : public T {
  public:
@@ -89,6 +90,8 @@ class CanvasPaintT : public T {
       // Cause a deliberate crash;
       CHECK(false);
     }
+    // No need to clear the canvas, because cairo automatically performs the
+    // clear.
 
     // Need to translate so that the dirty region appears at the origin of the
     // surface.
diff --git a/skia/ext/canvas_paint_mac.h b/skia/ext/canvas_paint_mac.h
index d679116..1f5ff03 100644
--- a/skia/ext/canvas_paint_mac.h
+++ b/skia/ext/canvas_paint_mac.h
@@ -17,6 +17,7 @@ namespace skia {
 // A class designed to translate skia painting into a region to the current
 // graphics context.  On construction, it will set up a context for painting
 // into, and on destruction, it will commit it to the current context.
+// Note: The created context is always inialized to (0, 0, 0, 0).
 template <class T>
 class CanvasPaintT : public T {
  public:
@@ -89,6 +90,7 @@ class CanvasPaintT : public T {
       // Cause a deliberate crash;
       *(volatile char*) 0 = 0;
     }
+    canvas->clear(SkColorSetARGB(0, 0, 0, 0));
 
     // Need to translate so that the dirty region appears at the origin of the
     // surface.
diff --git a/skia/ext/canvas_paint_wayland.h b/skia/ext/canvas_paint_wayland.h
index eca3665..bceb8bb 100644
--- a/skia/ext/canvas_paint_wayland.h
+++ b/skia/ext/canvas_paint_wayland.h
@@ -15,6 +15,7 @@ namespace skia {
 // A class designed to translate skia painting into a region in a Wayland window
 // surface. On construction, it will set up a context for painting into, and on
 // destruction, it will commit it to the Wayland window surface.
+// Note: The created context is always inialized to (0, 0, 0, 0).
 template <class T>
 class CanvasPaintT : public T {
  public:
@@ -86,6 +87,8 @@ class CanvasPaintT : public T {
       // Cause a deliberate crash;
       CHECK(false);
     }
+    // No need to clear the canvas, because cairo automatically performs the
+    // clear.
 
     // Need to translate so that the dirty region appears at the origin of the
     // surface.
diff --git a/skia/ext/canvas_paint_win.h b/skia/ext/canvas_paint_win.h
index 9610025..a9651d3 100644
--- a/skia/ext/canvas_paint_win.h
+++ b/skia/ext/canvas_paint_win.h
@@ -29,6 +29,7 @@ namespace skia {
 //     }
 //     return 0;
 //   }
+// Note: The created context is always inialized to (0, 0, 0, 0).
 template <class T>
 class CanvasPaintT : public T {
  public:
@@ -113,6 +114,7 @@ class CanvasPaintT : public T {
       // Cause a deliberate crash;
       *(char*) 0 = 0;
     }
+    canvas->clear(SkColorSetARGB(0, 0, 0, 0));
 
     // This will bring the canvas into the screen coordinate system for the
     // dirty rect
diff --git a/skia/ext/canvas_paint_x.h b/skia/ext/canvas_paint_x.h
index e8e3c68..a714a2e 100644
--- a/skia/ext/canvas_paint_x.h
+++ b/skia/ext/canvas_paint_x.h
@@ -17,6 +17,7 @@ namespace skia {
 // A class designed to translate skia painting into a region in a Wayland window
 // surface. On construction, it will set up a context for painting into, and on
 // destruction, it will commit it to the Wayland window surface.
+// Note: The created context is always inialized to (0, 0, 0, 0).
 template <class T>
 class CanvasPaintT : public T {
  public:
@@ -88,6 +89,8 @@ class CanvasPaintT : public T {
       // Cause a deliberate crash;
       CHECK(false);
     }
+    // No need to clear the canvas, because cairo automatically performs the
+    // clear.
 
     // Need to translate so that the dirty region appears at the origin of the
     // surface.