Use CheckedNumeric for size calculation in TextureGL.

Wrap the multiplication of width, height, and pixelBytes with
angle::CheckedNumeric to prevent potential integer overflow when
calculating the size for the zero-filled buffer.

This is speculative fix for the potential bug linked below.

See (sorry internal only): go/code-terracotta-reviewer-explainer for
details.

Bug:b/495363705
Change-Id: I3651b86f06d6acf9cf048c06c4acaeb6ba8ce2ac
Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/7696452
Commit-Queue: Geoff Lang <geofflang@chromium.org>
Auto-Submit: Stephen Nusko <nuskos@chromium.org>
Reviewed-by: Geoff Lang <geofflang@chromium.org>
Reviewed-by: Shahbaz Youssefi <syoussefi@chromium.org>

src/libANGLE/renderer/gl/TextureGL.cpp

diff --git a/src/libANGLE/renderer/gl/TextureGL.cpp b/src/libANGLE/renderer/gl/TextureGL.cpp
index 05299c9..c91c6ac 100644
--- a/src/libANGLE/renderer/gl/TextureGL.cpp
+++ b/src/libANGLE/renderer/gl/TextureGL.cpp
@@ -744,10 +744,14 @@
         const gl::InternalFormat &initFormatInfo =
             gl::GetInternalFormatInfo(initTexImageFormat.format, initTexImageFormat.type);
         GLuint pixelBytes = initFormatInfo.pixelBytes;
+        // TODO(b/495363705): Validate if this CheckedNumeric is required, remove either this TODO
+        // or the CheckedNumeric based on the result.
+        angle::CheckedNumeric<size_t> checkedBufferSize = angle::base::CheckMul(
+            angle::base::CheckMul(sourceArea.width, sourceArea.height), pixelBytes);
+        ANGLE_CHECK_GL_MATH(contextGL, checkedBufferSize.IsValid());
         angle::MemoryBuffer *zero;
-        ANGLE_CHECK_GL_ALLOC(
-            contextGL,
-            context->getZeroFilledBuffer(sourceArea.width * sourceArea.height * pixelBytes, &zero));
+        ANGLE_CHECK_GL_ALLOC(contextGL,
+                             context->getZeroFilledBuffer(checkedBufferSize.ValueOrDie(), &zero));
 
         gl::PixelUnpackState unpack;
         unpack.alignment = 1;