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, 19 deletions

diff --git a/src/gpu/GrGpu.cpp b/src/gpu/GrGpu.cpp
index bea6a601e6..eb005d110a 100644
--- a/src/gpu/GrGpu.cpp
+++ b/src/gpu/GrGpu.cpp
@@ -94,16 +94,12 @@ static bool check_texture_creation_params(const GrCaps& caps, const GrSurfaceDes
     }
 
     *isRT = SkToBool(desc.fFlags & kRenderTarget_GrSurfaceFlag);
-    if (*isRT && !caps.isConfigRenderable(desc.fConfig, desc.fSampleCnt > 1)) {
-        return false;
-    }
-
-    if (desc.fSampleCnt < 1) {
+    if (*isRT && !caps.isConfigRenderable(desc.fConfig, desc.fSampleCnt > 0)) {
         return false;
     }
 
     // We currently do not support multisampled textures
-    if (!*isRT && desc.fSampleCnt > 1) {
+    if (!*isRT && desc.fSampleCnt > 0) {
         return false;
     }
 
@@ -135,14 +131,9 @@ sk_sp<GrTexture> GrGpu::createTexture(const GrSurfaceDesc& origDesc, SkBudgeted
         return nullptr;
     }
 
-    if (isRT) {
-        desc.fSampleCnt = caps->getSampleCount(desc.fSampleCnt, desc.fConfig);
-        if (!desc.fSampleCnt) {
-            return nullptr;
-        }
-    }
+    desc.fSampleCnt = caps->getSampleCount(desc.fSampleCnt, desc.fConfig);
     // Attempt to catch un- or wrongly initialized sample counts.
-    SkASSERT(desc.fSampleCnt > 0 && desc.fSampleCnt <= 64);
+    SkASSERT(desc.fSampleCnt >= 0 && desc.fSampleCnt <= 64);
 
     if (mipLevelCount && (desc.fFlags & kPerformInitialClear_GrSurfaceFlag)) {
         return nullptr;
@@ -188,11 +179,8 @@ sk_sp<GrTexture> GrGpu::wrapBackendTexture(const GrBackendTexture& backendTex,
 sk_sp<GrTexture> GrGpu::wrapRenderableBackendTexture(const GrBackendTexture& backendTex,
                                                      int sampleCnt, GrWrapOwnership ownership) {
     this->handleDirtyContext();
-    if (sampleCnt < 1) {
-        return nullptr;
-    }
     if (!this->caps()->isConfigTexturable(backendTex.config()) ||
-        !this->caps()->isConfigRenderable(backendTex.config(), sampleCnt > 1)) {
+        !this->caps()->isConfigRenderable(backendTex.config(), sampleCnt > 0)) {
         return nullptr;
     }
 
@@ -209,7 +197,7 @@ sk_sp<GrTexture> GrGpu::wrapRenderableBackendTexture(const GrBackendTexture& bac
 }
 
 sk_sp<GrRenderTarget> GrGpu::wrapBackendRenderTarget(const GrBackendRenderTarget& backendRT) {
-    if (!this->caps()->isConfigRenderable(backendRT.config(), backendRT.sampleCnt() > 1)) {
+    if (!this->caps()->isConfigRenderable(backendRT.config(), backendRT.sampleCnt() > 0)) {
         return nullptr;
     }
     this->handleDirtyContext();
@@ -219,7 +207,7 @@ sk_sp<GrRenderTarget> GrGpu::wrapBackendRenderTarget(const GrBackendRenderTarget
 sk_sp<GrRenderTarget> GrGpu::wrapBackendTextureAsRenderTarget(const GrBackendTexture& tex,
                                                               int sampleCnt) {
     this->handleDirtyContext();
-    if (!this->caps()->isConfigRenderable(tex.config(), sampleCnt > 1)) {
+    if (!this->caps()->isConfigRenderable(tex.config(), sampleCnt > 0)) {
         return nullptr;
     }
     int maxSize = this->caps()->maxTextureSize();