Revert "Redefine the meaning of sample counts in GPU backend."

This reverts commit 48825b11ad25c98b9a4884d5cc0edd4e290c4409.

Reason for revert: nanobench

Original change's description:
> Redefine the meaning of sample counts in GPU backend.
> 
> Old: 0  -> nonMSAA
>      1+ -> MSAA
> 
> New:
>      0  -> error/unsupported
>      1  -> nonMSAA
>      2+ -> MSAA
> 
> We still allow 0 to mean nonMSAA in three sets of public APIs for backwards compatibility:
> 
> 1) SkSurface factories
> 2) GrBackendRenderTarget constructors
> 3) GrCaps::getSampleCnt()'s requestedCount parameter
> 
> However, we immediately clamp to 1 and treat 0 as invalid/non-renderable internally.
> 
> This also changes the behavior when using a large sample count. We now fail in that case rather than using the largest sample available sample count. GrCaps::getSampleCount() will return 0 in this case.
> 
> 
> Bug: skia:
> Change-Id: Ida22c6b22c1365e563c9046b611e88bf5eb3ff33
> Reviewed-on: https://skia-review.googlesource.com/101560
> Reviewed-by: Greg Daniel <egdaniel@google.com>
> Commit-Queue: Brian Salomon <bsalomon@google.com>

TBR=egdaniel@google.com,bsalomon@google.com

Change-Id: Ic257619a8a5ee9ac15419ecf10259e42daed7f82
No-Presubmit: true
No-Tree-Checks: true
No-Try: true
Bug: skia:
Reviewed-on: https://skia-review.googlesource.com/102662
Reviewed-by: Brian Salomon <bsalomon@google.com>
Commit-Queue: Brian Salomon <bsalomon@google.com>

1 files changed, 7 insertions, 8 deletions

diff --git a/tools/viewer/Viewer.cpp b/tools/viewer/Viewer.cpp
index 35b0e146f9..198f9baab6 100644
--- a/tools/viewer/Viewer.cpp
+++ b/tools/viewer/Viewer.cpp
@@ -78,7 +78,7 @@ static DEFINE_string(jsons, "jsons", "Directory to read (Bodymovin) jsons from."
 
 static DEFINE_string2(backend, b, "sw", "Backend to use. Allowed values are " BACKENDS_STR ".");
 
-static DEFINE_int32(msaa, 1, "Number of subpixel samples. 0 for no HW antialiasing.");
+static DEFINE_int32(msaa, 0, "Number of subpixel samples. 0 for no HW antialiasing.");
 
 DECLARE_int32(threads)
 
@@ -501,7 +501,7 @@ void Viewer::updateTitle() {
     if (!fWindow) {
         return;
     }
-    if (fWindow->sampleCount() < 1) {
+    if (fWindow->sampleCount() < 0) {
         return; // Surface hasn't been created yet.
     }
 
@@ -561,8 +561,7 @@ void Viewer::updateTitle() {
 
     title.append(" [");
     title.append(kBackendTypeStrings[fBackendType]);
-    int msaa = fWindow->sampleCount();
-    if (msaa > 1) {
+    if (int msaa = fWindow->sampleCount()) {
         title.appendf(" MSAA: %i", msaa);
     }
     title.append("]");
@@ -995,7 +994,7 @@ void Viewer::drawImGui() {
                 if (ctx) {
                     int sampleCount = fWindow->sampleCount();
                     ImGui::Text("MSAA: "); ImGui::SameLine();
-                    ImGui::RadioButton("1", &sampleCount, 1); ImGui::SameLine();
+                    ImGui::RadioButton("0", &sampleCount, 0); ImGui::SameLine();
                     ImGui::RadioButton("4", &sampleCount, 4); ImGui::SameLine();
                     ImGui::RadioButton("8", &sampleCount, 8); ImGui::SameLine();
                     ImGui::RadioButton("16", &sampleCount, 16);
@@ -1019,7 +1018,7 @@ void Viewer::drawImGui() {
 
                     if (!ctx) {
                         ImGui::RadioButton("Software", true);
-                    } else if (fWindow->sampleCount() > 1) {
+                    } else if (fWindow->sampleCount()) {
                         prButton(GpuPathRenderers::kDefault);
                         prButton(GpuPathRenderers::kAll);
                         if (ctx->caps()->shaderCaps()->pathRenderingSupport()) {
@@ -1199,7 +1198,7 @@ void Viewer::updateUIState() {
     if (!fWindow) {
         return;
     }
-    if (fWindow->sampleCount() < 1) {
+    if (fWindow->sampleCount() < 0) {
         return; // Surface hasn't been created yet.
     }
 
@@ -1245,7 +1244,7 @@ void Viewer::updateUIState() {
     const GrContext* ctx = fWindow->getGrContext();
     if (!ctx) {
         prState[kOptions].append("Software");
-    } else if (fWindow->sampleCount() > 1) {
+    } else if (fWindow->sampleCount()) {
         prState[kOptions].append(gPathRendererNames[GpuPathRenderers::kDefault]);
         prState[kOptions].append(gPathRendererNames[GpuPathRenderers::kAll]);
         if (ctx->caps()->shaderCaps()->pathRenderingSupport()) {