Various fixes for wide color gamut rendering

This CL addresses multiple issues:
- A logic issue where the wide gamut color mode was not set at the right time
- The presence of scRGB surfaces was not detected
- The sRGB to Display P3 matrix was transposed
- The color matrix was applied in gamma space instead of linear space*
- The GPU code path was doing a division by w for each pixel when a
  color transform is set, which shouldn't be necessary (the code now
  checks that the matrix has the expected form)
- Incorrect comment
- Dead code in Description.cpp (mDirtyUniforms was never used)
- Screenshots were taken using the last render engine configuration,
  the configuration is now properly set every time

* This can in theory cause a discrepancy when we switch to/from hardware
  composer mode. I was not able to create a visible discrepancy in practice
  using Night Light, color blindness compensation modes and color inversion.
  More importantly, how/where the hardware composer applies the color
  transform is not specified: it could be gamma or linear space, before or
  after the hardware color LUT. We'll address this in a future CL if needed.
  In addition, this code assumes that fp16 surfaces are encoded in non-linear
  space (scRGB-nl instead of scRGB) but we do not have EGL/Vulkan extensions
  to specify this behavior. We need to address this as well

This CL also fixes potential divides by 0 in the GPU code path.

Bug: 29940137
Test: CtsUiRenderingTestsCases, CtsGraphicsTestCases

Change-Id: I9ae15850f8b9d48c39ebc2724ca3da202be9b008
diff --git a/libs/gui/SurfaceComposerClient.cpp b/libs/gui/SurfaceComposerClient.cpp
index 8c83843..7ae2672 100644
--- a/libs/gui/SurfaceComposerClient.cpp
+++ b/libs/gui/SurfaceComposerClient.cpp
@@ -1080,5 +1080,9 @@
     return mBuffer.stride * mBuffer.height * bytesPerPixel(mBuffer.format);
 }
 
+android_dataspace ScreenshotClient::getDataSpace() const {
+    return mBuffer.dataSpace;
+}
+
 // ----------------------------------------------------------------------------
 }; // namespace android
diff --git a/libs/math/include/math/TMatHelpers.h b/libs/math/include/math/TMatHelpers.h
index 5cb725d..1423ade 100644
--- a/libs/math/include/math/TMatHelpers.h
+++ b/libs/math/include/math/TMatHelpers.h
@@ -342,9 +342,9 @@
 template <typename MATRIX>
 String8 asString(const MATRIX& m) {
     String8 s;
-    for (size_t c = 0; c < MATRIX::col_size(); c++) {
+    for (size_t c = 0; c < MATRIX::COL_SIZE; c++) {
         s.append("|  ");
-        for (size_t r = 0; r < MATRIX::row_size(); r++) {
+        for (size_t r = 0; r < MATRIX::ROW_SIZE; r++) {
             s.appendFormat("%7.2f  ", m[r][c]);
         }
         s.append("|\n");